California

California Fire Map: How to Track California Wildfires Live, County by County

📅 September 2026 ⏱ 61 min read ✍ US Wildfire Tracker team

A California fire map is a live view of every wildfire burning in the state, built from CAL FIRE and federal incident records, official perimeters, satellite heat detections and National Weather Service fire-weather alerts. Read together, those four layers tell you where a fire is, how big it is and whether it is moving toward you.

What does a California fire map actually show you?

A California fire map shows four distinct things at once: incident records published by fire agencies, mapped fire perimeters, satellite heat detections, and weather alerts. Each answers a different question. Confusing one for another is the single most common mistake people make during a fast-moving California wildfire.

An incident record is the administrative object. When CAL FIRE or a federal agency opens a fire, that fire gets a name, a discovery date, an acreage figure, a containment percentage and a managing organization. CAL FIRE publishes ongoing emergency responses including all wildfires of 10 acres or more.

A perimeter is a polygon drawn around the burned area. It is produced by infrared aircraft, GPS units carried by crews, or satellite analysis, and it is only as fresh as the last flight or the last upload. A perimeter is history, not a forecast.

A satellite heat detection is a pixel where an instrument measured thermal energy consistent with fire. It is fast and it is coarse. VIIRS, the sensor most often used for wildfire work, has a 375-meter-per-pixel imager band, which is fine enough to catch small, cooler fires but far too coarse to show which street is burning.

A fire-weather alert is a forecast. National Weather Service Red Flag Warnings mark the hours when a new ignition in California is most likely to escape. CAL FIRE describes them as indicating warm temperatures, very low humidities and stronger winds that combine to raise fire danger.

Why one number is never enough

Acreage alone is a bad proxy for danger. The Camp Fire of November 2018 burned 153,336 acres in Butte County and destroyed 18,804 structures with 85 deaths, making it both the most destructive and the deadliest California wildfire on CAL FIRE's records. It does not appear in the top 20 by size.

The opposite case is just as instructive. The Rush Fire of August 2012 burned 271,911 acres in Lassen County and destroyed zero structures. It sits eleventh on CAL FIRE's largest-fires list. Size measures fuel and terrain; destruction measures where people built.

That is why a useful California fire map pairs acreage with containment, discovery age and location relative to communities. On the US Wildfire Tracker live map those fields sit together in one panel so you are never reading a headline acreage figure in isolation.

Who actually needs a California fire map

Residents in the wildland-urban interface use it to decide whether to pre-pack a vehicle. Commuters use it to decide whether Highway 101, Interstate 5 or State Route 299 will still be open tonight. Ranchers use it to decide when to start moving livestock, which is why California evacuation warnings explicitly call out people with large animals.

Journalists, insurance adjusters, land managers and school administrators use the same layers for different decisions. The layers do not change; the threshold for acting on them does. Our companion guide to the live US wildfire map covers the national view that sits behind the California one.

Which agencies feed a California fire map?

Five kinds of organization put data on a California fire map: CAL FIRE, the US Forest Service Pacific Southwest Region, county and city fire departments, the California Governor's Office of Emergency Services, and the National Weather Service. Each owns a different slice of the state and a different slice of the record.

CAL FIRE, the state agency

CAL FIRE is the California Department of Forestry and Fire Protection. Its firefighters protect over 31 million acres of California wildlands and provide emergency services in 36 of the state's 58 counties, according to the agency's own fire protection overview.

The land CAL FIRE is responsible for is called State Responsibility Area, or SRA. Land inside a city or a fire district is Local Responsibility Area. Land owned by the federal government is Federal Responsibility Area. Every California fire map inherits this three-way split, and it explains why some fires get a CAL FIRE incident page and others do not.

CAL FIRE is organised into two regions, Northern and Southern, subdivided into units that mostly follow county lines. The unit names read like a gazetteer of California fire country: Shasta-Trinity, Sonoma-Lake-Napa, Nevada-Yuba-Placer, Madera-Mariposa-Merced, San Benito-Monterey, Tuolumne-Calaveras, Fresno-Kings, Riverside, San Diego.

Treat CAL FIRE as the authoritative state data source and the agency whose orders you follow. It is not a substitute for a consolidated live map, because CAL FIRE publishes state-jurisdiction incidents and does not carry every federal fire in California in the same view.

The US Forest Service and other federal agencies

Federal lands make up 58 percent of California's forestlands, a figure the Governor's office cited in July 2026 when describing state investment in wildfire projects on federal ground. Fires on those lands are managed by the US Forest Service Pacific Southwest Region, the National Park Service, the Bureau of Land Management or the Fish and Wildlife Service.

Federal incidents flow into the national interagency record system that the National Interagency Fire Center publishes. That is the feed a national California fire map uses to show a Sierra Nevada or Klamath fire that never touches a CAL FIRE incident page. Wildfire tracking works the same way nationwide: an incident record opens, gets an identifier, and is updated by the managing agency until the fire is declared out.

Counties, cities and Cal OES

Evacuation orders in California are issued by law enforcement, usually a county sheriff or a city police department, not by the fire agency. County offices of emergency services publish evacuation zone polygons; municipal departments such as the Los Angeles Fire Department run their own brush patrol and incident communications.

Cal OES coordinates the state's mutual aid system. It manages a fleet of more than 270 state-owned fire engines assigned to over 60 local agencies statewide, and it runs the Fire Integrated Real-Time Intelligence System, which has flown over 2,000 missions since 2019 and supports every California county.

The National Weather Service

Six NWS forecast offices cover most of populated California: Eureka, Sacramento, San Francisco Bay Area, Hanford, Los Angeles/Oxnard and San Diego. They issue Red Flag Warnings and Fire Weather Watches, and they publish the wind forecasts that decide whether a new start becomes a 200-acre fire or a 20,000-acre one.

The NWS glossary sets out national Red Flag criteria: sustained wind averaging 15 mph or greater, relative humidity at or below 25 percent, and a temperature above 75 degrees Fahrenheit, on top of high to extreme fire danger after a dry spell. Local offices adapt thresholds to California terrain.

A California fire map that fuses all seven rows into a single view saves you from opening seven tabs during a wind event. That fusion is exactly what US Wildfire Tracker does, and the complete fire tracker guide explains the mechanics behind it.

How do you read every layer on a CA fire map?

A CA fire map stacks layers that update on completely different clocks. Read them in a fixed order: official incident first, perimeter second, satellite heat third, weather alert fourth, evacuation status last but loudest. Reading them out of order is how people talk themselves into staying put.

Layer one: the incident marker

The incident marker is the pin with a name. Behind it sits the record: fire name, discovery date, acres, percent contained, incident type, managing organization and, when the agency supplies it, total personnel assigned. On a CA fire map these fields come from the interagency record, so they match what the incident management team is reporting.

Containment is the field people misread most. Containment measures the share of the fire's edge that has a completed control line around it. A fire can be 60 percent contained and still make a major run through the uncontained 40 percent. Containment is not a measure of how much of the fire is out.

Discovery age matters as much as acreage. A 300-acre fire discovered 40 minutes ago in September grass is a very different object from a 300-acre fire that has been creeping through timber for nine days. US Wildfire Tracker surfaces discovery age directly so you do not have to subtract dates under pressure.

Layer two: the official perimeter

The perimeter polygon is drawn from the best available mapping: infrared aircraft at night, GPS tracks walked or driven by crews, or satellite-derived burned area. US Forest Service NIROPS aircraft carry an infrared sensor that maps 300,000 acres of terrain per hour and, from 10,000 feet, can detect a hotspot just 6 inches across and place it within 12.5 feet on a map.

Those flights happen at night, when there is no sun glint and the background is cooler. That single scheduling fact explains why a perimeter on your California fire map often looks stale at 4 p.m. and suddenly jumps at 6 a.m. The fire grew all afternoon; the map only learned about it after the aircraft flew.

CAL FIRE states plainly that perimeters "are generalized and do not necessarily indicate structures within the boundaries have been damaged or destroyed." A polygon over your neighborhood is not a report about your house.

Layer three: satellite heat detections

Two families of satellite feed a California fire map. Polar-orbiting instruments, MODIS on NASA's Terra and Aqua and VIIRS on the Suomi NPP and NOAA-20 series, pass overhead a few times a day at 375 metres to 1 kilometre resolution. Geostationary GOES satellites stare continuously at much coarser resolution.

NOAA states that its geostationary satellites scan new imagery over an area covering multiple states every minute and generate a fresh image of the entire contiguous United States every five minutes. That cadence is why GOES often flags a new California start before a polar satellite passes over it.

Satellite heat is a detection, not a fire. Industrial flares, steel plants, prescribed burns, agricultural burning in the Central Valley and even hot bare rock can trigger a thermal anomaly. This is why US Wildfire Tracker assigns each detection a fire probability score and hides weak signals below 25 percent by default.

Layer four: fire-weather alerts

Red Flag Warning polygons are the layer that tells you about tomorrow rather than today. The National Weather Service describes a Red Flag Warning as a "Take Action" product issued with land management agencies to flag an ongoing or imminent critical fire weather pattern, and a Fire Weather Watch as a "Be Prepared" alert for conditions that could produce extensive fire occurrence or extreme fire behavior.

In California these polygons often follow terrain rather than county lines, because the wind that matters is channelled through specific passes. A Red Flag Warning that covers the Santa Ana Mountains and the Cajon Pass but not coastal Orange County is not an error; it is the forecast being precise.

Layer five: evacuation status and road closures

Evacuation polygons are published by county sheriffs and offices of emergency services. They are the layer with legal force. Everything else on a California fire map informs your judgement; this layer replaces it. When an Evacuation Order covers your zone, the correct response is to leave, regardless of what the perimeter looks like.

For a layer-by-layer walkthrough with worked examples, our guide to reading a fire tracker map goes deeper on the cartography, and the live fire tracker latency guide covers exactly how fresh each feed is.

When do California wildfires peak, month by month?

California wildfires no longer respect a single season. CAL FIRE now declares fire season unit by unit, and three of its southern units, San Diego, Riverside and San Bernardino, are simply listed as "Year-Round" in the 2026 declarations. The rest of the calendar still follows a recognisable rhythm.

The 2026 declaration calendar

CAL FIRE's 2026 summer preparedness declarations show the season opening from south to north. Fresno-Kings declared on April 13, 2026. San Luis Obispo followed on May 1, San Benito-Monterey on May 18 and Madera-Mariposa-Merced on May 22. Most northern units declared on June 1, with Tuolumne-Calaveras last on June 15.

January to March: the wind-driven winter window

Winter used to be the safe part of the California fire map. It is not. The Eaton and Palisades fires both started in January 2025 in Los Angeles County and now sit second and third on CAL FIRE's most destructive list, with 9,413 and 6,833 structures destroyed respectively.

The mechanism is simple: if the winter rains are late, coastal Southern California fuels stay dry while offshore wind season is at its peak. The National Weather Service notes that Santa Ana winds are most common during December, and they continue through the winter months.

April to June: grass cures and the south opens

Annual grasses cure from the south and the low elevations upward. Fresno-Kings declaring in mid-April and San Luis Obispo on May 1 track that curing front. Grass fires in this window are fast but usually shallow-rooted, and initial attack contains most of them within hours.

This is also the window when a California fire map fills with small incidents that never make the news. CAL FIRE's own note is that the majority of fires within its jurisdiction are contained quickly, and fires under 10 acres generally do not get published incident pages at all.

July to September: the peak of California wildfires

July through September is when the largest California wildfires historically start. Of CAL FIRE's twenty largest fires, fourteen began in July or August, including the Dixie Fire (July 2021, 963,309 acres), the Mendocino Complex (July 2018, 459,123 acres) and the Park Fire (July 2024, 429,603 acres).

Lightning is a major driver in this window. Seven of the twenty largest California fires are attributed to lightning, including the August Complex, the SCU Lightning Complex and the North Complex, all of which ignited in August 2020 during a single extraordinary dry-lightning outbreak.

October to December: the wind months

Autumn is when the fuel is driest and the offshore winds arrive. Seven of CAL FIRE's twenty most destructive fires started in October: Tubbs (5,636 structures), Tunnel in the Oakland hills (2,900), Cedar (2,820), Witch (1,650), Nuns (1,355), Old (1,003) and Jones (954). The Camp Fire started in November; the Thomas Fire started in December.

The season ends when the rain arrives, not on a calendar date. NIFC's September 2026 outlook expects the first storm out of the Gulf of Alaska to arrive before the first Santa Ana wind event this autumn, and forecasts near-normal significant fire potential across central and southern California from September through December.

NIFC's September 2026 outlook also gives a sense of routine tempo in the north: Red Flag Warnings were issued on 10 separate days in August 2026 across northern California, almost exactly the August average of 10.1 days measured from 2006 to 2025. Northern California averaged 15.1 new ignitions per day through August 26.

How do California wildfires differ by region?

California wildfires behave like four different hazards depending on where they burn. The northern mountains produce the largest acreages. The Sierra Nevada produces long-duration timber fires. The Central Coast produces wind-and-terrain fires in chaparral. Southern California produces the fires that destroy the most homes fastest.

The four fire provinces

The simplest way to use a California fire map is to know which province you are looking at before you interpret an acreage number. A 40,000-acre fire in Trinity County and a 40,000-acre fire in Los Angeles County are not comparable events, even though the marker on the map looks identical.

Why the same tool works everywhere

The layers do not change between provinces; the thresholds do. In the northern mountains, a fire 15 miles away with no wind forecast is usually a smoke problem, not an evacuation problem. In Malibu during a Santa Ana event, a fire 15 miles upwind is an immediate planning problem.

A national tool with a state filter handles both cases. US Wildfire Tracker lets you switch between a national view and any of the 50 states plus DC, or use browser geolocation to show only fires within a set distance in miles from where you are standing.

Where the smoke goes is a separate question

Smoke does not obey province boundaries. Smoke from a Klamath complex regularly reaches the Sacramento Valley and the Bay Area, and Central Valley inversions can trap it for days. The EPA's Air Quality Index runs from Good (0 to 50) through Moderate (51 to 100) to Hazardous (301 and higher), and California routinely sees the upper categories during large fires.

That is why smoke belongs on its own layer rather than being inferred from fire location. Our forest fire smoke tracker guide covers plume analysis, PM2.5 and the health thresholds by group.

Why do Northern California wildfires burn so large?

Northern California wildfires produce the state's biggest acreages because three conditions line up: enormous continuous fuel beds, terrain that firefighters cannot easily reach, and dry-lightning outbreaks that start dozens of fires at once. The result is complexes rather than single fires.

The complex is the defining unit

A complex is two or more fires managed under one incident organisation. Seven of CAL FIRE's twenty largest fires are complexes, and they dominate the top of the list. The August Complex of August 2020 reached 1,032,648 acres across seven counties: Mendocino, Humboldt, Trinity, Tehama, Glenn, Lake and Colusa.

On a California fire map a complex looks confusing, because the incident record carries a single acreage while satellite heat appears in several disconnected clusters. That is not a data error. It is one administrative object covering many separate fire fronts, sometimes 60 miles apart.

Trinity County is the recurring name

By our count of CAL FIRE's published Top 20 Largest list, Trinity County appears in four of the twenty largest California wildfires: the August Complex, the Carr Fire, the Monument Fire and the River Complex. No other county appears more often on that list.

Trinity is instructive because it explains the difference between size and consequence. The Monument Fire of August 2021 burned 223,124 acres and destroyed 28 structures. The Carr Fire of July 2018 burned 229,651 acres, a nearly identical figure, and destroyed 1,614 structures with 8 deaths, because it ran into Redding in Shasta County.

The 2020 lightning siege as a worked example

August 2020 remains the clearest illustration of how northern California fills a fire map overnight. Four fires from that single month sit in the top eight by size: the August Complex (1,032,648 acres), the SCU Lightning Complex (396,625 acres), the LNU Lightning Complex (363,220 acres) and the North Complex (318,935 acres).

The SCU Lightning Complex alone spanned Stanislaus, Santa Clara, Alameda, Contra Costa and San Joaquin counties. The LNU Lightning Complex spanned Napa, Solano, Sonoma, Yolo, Lake and Colusa, destroyed 1,491 structures and killed 6 people. Across California that year, over 9,000 wildfires burned over 4.2 million acres.

Powerlines and the northern Sierra foothills

CAL FIRE attributes the second-largest California fire, the Dixie Fire of July 2021, to powerlines. It burned 963,309 acres across Butte, Plumas, Lassen, Shasta and Tehama counties and destroyed 1,311 structures. The Camp Fire of November 2018, also attributed to powerlines, burned about a sixth of that acreage and destroyed fourteen times as many buildings.

That pairing is the single most useful lesson a northern California fire map can teach. Ignition source predicts where a fire starts; wind and settlement pattern predict what it costs. Both fires started in Butte County, less than three years apart.

What to watch in the north

1. Check whether the incident is a complex. If the name ends in "Complex", expect scattered heat and a single combined acreage.
2. Compare acreage against structures destroyed. Large northern fires often destroy very few buildings, and that changes your urgency.
3. Look for lightning activity in the days before ignition, because holdover fires can surface a week after the storm.
4. Check the containment trend across two days rather than the containment number today.
5. Watch the smoke layer separately; northern smoke reaches Sacramento and the Bay Area routinely.

How do Sierra and Central Coast California fires burn?

Sierra Nevada and Central Coast California fires occupy the middle of the state's hazard spectrum. Sierra fires are long-duration timber events in steep terrain with heavy federal involvement. Central Coast fires are chaparral and grass fires that turn dangerous when a wind event lines up with cured fuel.

The Sierra Nevada: elevation decides everything

Sierra fires climb. The Creek Fire of September 2020 burned 379,895 acres across Fresno and Madera counties and destroyed 858 structures, making it the sixth-largest California wildfire on CAL FIRE's list. The Rim Fire of August 2013 burned 257,314 acres in Tuolumne County, much of it inside Stanislaus National Forest and Yosemite National Park.

Because so much Sierra land is federal, a Sierra incident may never appear on a state incident page at all. A California fire map that only carries CAL FIRE records will show a blank where a 200,000-acre federal fire is burning. This is the strongest practical argument for a fused state and federal view.

The Caldor Fire of August 2021 is the Sierra fire people remember, because it crossed the Sierra crest and reached the edge of the Lake Tahoe basin. It burned 221,835 acres across Alpine, Amador and El Dorado counties and destroyed just over 1,000 structures.

Central Coast: chaparral, marine layer and terrain

The Central Coast runs from San Mateo County down through Santa Cruz, Monterey, San Luis Obispo and Santa Barbara. Fuel is a mosaic of coastal grass, chaparral, oak woodland and, in the Santa Cruz Mountains, redwood. The marine layer suppresses fire behavior most days and then withdraws.

The CZU Lightning Complex of August 2020 burned 86,509 acres across Santa Cruz and San Mateo counties and destroyed 1,490 structures, placing it fourteenth on CAL FIRE's most destructive list despite modest acreage. Redwood forest is not fireproof when the fuel underneath it is cured and the humidity collapses.

Santa Barbara County contributes two entries to the largest-fires list: the Zaca Fire of July 2007 at 240,207 acres, which destroyed a single structure, and the Thomas Fire of December 2017 at 281,893 acres shared with Ventura County, which destroyed 1,060.

Monterey County in the 2026 season

As of September 10, 2026, the two largest active incidents on CAL FIRE's California fire map were both in Monterey County: the Plaskett Fire, started August 26, 2026, at 29,885 acres and 61 percent contained, and the Timber Fire, started August 8, 2026, at 25,380 acres and 27 percent contained.

Both are typical Central Coast events: they started in late summer, they burn in steep coastal terrain with limited road access, and their containment percentages climbed slowly over weeks rather than days. Watching a pair like this over several days is the best way to learn how containment actually behaves.

The Central Valley in between

The Central Valley itself rarely produces headline fires, but it produces a great deal of noise on a satellite layer. Agricultural burning, food-processing plants and industrial heat sources all register as thermal anomalies. A California fire map that shows every raw detection will paint the valley with pins that are not fires.

This is exactly the problem the fire probability score solves. US Wildfire Tracker fuses whether an official record is linked, how fresh the official perimeter is, and how recent the VIIRS, MODIS or GOES heat is into a single tier, then hides weak signals below 25 percent unless you ask to see them.

What makes Southern California fires so destructive?

Southern California fires destroy more homes per acre than anywhere else in the state because three things coincide: continuous chaparral that carries fire at extreme rates of spread, offshore winds that arrive when fuel moisture is at its annual minimum, and dense housing built directly against the fuel.

The arithmetic of destruction

Compare two entries on CAL FIRE's most destructive list. The Eaton Fire of January 2025 burned 14,021 acres in Los Angeles County and destroyed 9,413 structures with 19 deaths. The Dixie Fire burned 963,309 acres, roughly 69 times as much ground, and destroyed 1,311 structures.

That is a difference of nearly three orders of magnitude in structures destroyed per acre. Acreage on a California fire map tells you about vegetation. Structures destroyed tells you about the wildland-urban interface, and Southern California has more of it in the path of wind-driven fire than any comparable landscape in the United States.

Los Angeles and Ventura counties

Los Angeles County holds three entries on CAL FIRE's Top 20 Deadliest list from before the modern era alone: Griffith Park in October 1933 with 29 deaths on just 47 acres, the Loop Fire of November 1966 with 12 deaths, and the Canyon Fire of August 1968 with 8. Add Eaton and Palisades from January 2025 and the county carries five of the twenty deadliest.

Ventura County supplies the Thomas Fire (December 2017, 281,893 acres shared with Santa Barbara), the Woolsey Fire (November 2018, 96,949 acres and 1,643 structures) and the Matilija Fire of September 1932, which at 220,000 acres is the oldest entry on the largest-fires list.

If you live in Los Angeles County, the detailed metro breakdown in our LA fires map guide covers the Santa Monica Mountains, the San Gabriels, Malibu, the Altadena and Pasadena foothills, Santa Clarita and the freeway closure patterns that follow each corridor.

San Diego, Riverside and San Bernardino

San Diego County appears twice in the twenty largest California fires, with the Cedar Fire of October 2003 at 273,246 acres and the Witch Fire of October 2007 at 197,990 acres. It also carries four entries on the deadliest list: Cedar with 15 deaths, Hauser Creek in October 1943 with 11, Inaja in November 1956 with 11 and Harris in October 2007 with 8.

San Bernardino County contributes the Old Fire of October 2003, 91,281 acres, 1,003 structures and 6 deaths. All three of these counties, San Diego, Riverside and San Bernardino, are the units CAL FIRE lists as Year-Round rather than seasonal, which is the clearest official statement that Southern California no longer has an off season.

Chaparral does not behave like forest

Chaparral is a dense, resinous, even-aged shrub fuel. Under a strong offshore wind it produces rates of spread and ember cast that forest fuels rarely match, and it recovers by resprouting and seeding after fire, so the fuel returns within a decade. A California fire map cannot show you fuel type, but knowing the province tells you what to expect.

NIFC's September 2026 outlook reported live fuel moisture across central and southern California mostly between 60 and 80 percent, slightly below normal for the time of year. Live fuel moisture below roughly 60 percent is the threshold fire managers watch most closely in chaparral country.

How do Santa Ana winds change a California fire map?

Santa Ana winds turn a routine Southern California ignition into a conflagration by supplying wind speed, low humidity and downslope heating at the same time. During a Santa Ana event, the perimeter layer on a California fire map falls hours behind reality, and the Red Flag layer becomes the one that matters.

The mechanism, in official terms

The National Weather Service glossary defines a Santa Ana wind as a condition "in which strong, hot, dust-bearing winds descend to the Pacific Coast around Los Angeles from inland desert regions." NWS San Diego's Weather Guide describes them as strong, dry offshore winds from the east or northeast, strongest below the passes and canyons of the Southern California coastal ranges.

They develop when high pressure builds over the Great Basin, the plateau east of the Sierra Nevada and west of the Rockies. Air flows from that high pressure toward lower pressure at the coast, descending thousands of feet. Compression heats it, relative humidity collapses, and the flow accelerates through topographic gaps.

The numbers that matter

NWS San Diego states that a reasonably strong Santa Ana event produces sustained wind speeds of 30 to 40 mph with gusts over 60 mph, and that during exceptional events the top gusts can exceed 100 mph. National Weather Service safety messaging notes these winds "can easily exceed 40 miles per hour" and "can severely exacerbate brush or forest fires, especially under drought conditions."

The timing detail is the one most people miss. NWS San Diego notes that "the strongest winds usually occur during the night and morning due to the absence of a competing sea breeze." That is exactly when perimeter mapping flights are least likely to have flown recently, and exactly when a California fire map is most likely to be out of date.

Santa Ana fires on the record

The largest and most destructive fires in Southern California history cluster in the Santa Ana months. The Cedar and Witch fires both started in October, in San Diego County. The Thomas Fire started in December 2017 in Ventura County. The Woolsey Fire started in November 2018. Eaton and Palisades both started in January 2025.

What these events share is not the ignition source, which ranges from powerlines to arson to human activity, but the wind. CAL FIRE attributes Thomas and Witch to powerlines, Woolsey and Eaton to electrical causes, Cedar to human-related activity and Palisades to arson. The wind is the common multiplier.

How to use the map during a Santa Ana event

1. Open the Red Flag Warning layer before you look at fire markers, and note when the warning starts and ends.
2. Identify which pass or canyon the forecast wind is channelled through, because fire will run downwind from there.
3. Treat any new heat detection upwind of you as significant even if no official record exists yet.
4. Check the "last satellite heat" timestamp rather than the perimeter, which will be lagging.
5. Confirm your evacuation zone status directly with your county sheriff or office of emergency services.
6. Plan a route that does not require driving toward or across the wind-aligned fire spread direction.

How do Diablo winds fuel Northern California fires?

Diablo winds are Northern California's offshore wind regime, and they drive the Bay Area and North Bay fires that fill a California fire map every autumn. The National Weather Service glossary describes them as similar to Santa Ana winds, occurring below canyons in the East Bay hills of the Diablo Range.

Definition and mechanism

According to the NWS glossary entry for Diablo wind, they "develop due to high pressure over Nevada and lower pressure along the central California coast" and "in extreme cases can exceed 60 mph." The physical mechanism is the same as a Santa Ana: descent, compression, heating, humidity collapse and channelling through terrain gaps.

The geography differs. Where Santa Ana winds funnel through the Cajon Pass, the Santa Ana Canyon and the passes of the Transverse Ranges, Diablo winds pour off the Diablo Range and the northern Coast Ranges into Sonoma, Napa, Lake, Solano, Contra Costa and Alameda counties.

The October fires of the North Bay

October 2017 is the reference event. The Tubbs Fire burned 36,807 acres across Napa and Sonoma counties, destroyed 5,636 structures and killed 22 people, placing it fourth on CAL FIRE's most destructive list. The same wind event produced the Nuns Fire in Sonoma (54,382 acres, 1,355 structures), the Atlas Fire in Napa and Solano (51,624 acres, 781 structures, 6 deaths) and the Redwood Valley Fire in Mendocino (36,523 acres, 544 structures, 9 deaths).

Two years earlier, the Valley Fire of September 2015 burned 76,067 acres across Lake, Napa and Sonoma counties and destroyed 1,955 structures. Three years later, the Glass Fire of September 2020 burned 67,484 acres in Napa and Sonoma and destroyed 1,520.

What Diablo events do to the map

Diablo wind fires start in the dark and run downhill toward valley floors where people live. The Tunnel Fire of October 1991 in Alameda County, which destroyed 2,900 structures on just 1,600 acres and killed 25 people, is the extreme case: an urban conflagration in the Oakland hills that barely registers as a wildfire by acreage.

On a California fire map that means two things. First, expect the perimeter to lag badly overnight. Second, expect the ratio of structures destroyed to acres burned to be far higher than in the northern mountains, so treat any North Bay or East Bay ignition during a wind advisory as significant regardless of its reported size.

Which California wildfires were the largest ever?

CAL FIRE publishes a Top 20 Largest California Wildfires list, and it is the reference every California fire map discussion should start from. The list is led by the August Complex at 1,032,648 acres and ends with the Klamath Theater Complex at 192,038 acres.

The full top 20 by acreage

CAL FIRE notes two caveats on the list itself. It excludes jurisdiction, so the ranking mixes state, federal and local responsibility fires. And it treats records before 1932 as less reliable, so the list is an overview of the large fires of recent times rather than an all-time register.

What the list tells you about timing

Fourteen of the twenty largest California wildfires started in July or August. Two started in September, two in October, one in June and one in December. Only the Thomas Fire, which started in December 2017, falls in the traditional winter, and it did so during a Santa Ana event on fuel that had not seen rain.

Nine of the twenty started in either 2020 or 2021. The August Complex, SCU, LNU, North Complex and Creek fires all belong to 2020; Dixie, Monument, Caldor and the River Complex all belong to 2021. That two-year cluster reshaped what "normal" looks like on a California fire map.

What the list tells you about cause

CAL FIRE attributes seven of the twenty largest fires to lightning, five to human-related activity, three to powerlines, one to arson and one to lightning combined with arson, leaving three undetermined or under investigation. Lightning dominates the very large northern complexes; powerlines dominate the destructive ones.

The Cal OES and CAL FIRE prevention campaign states that human activity causes an estimated 95 percent of wildfires. That figure covers all fires, not just the largest, and it is the reason prevention messaging focuses on ignition sources rather than on fuel.

Context from the national record

California's biggest years sit inside a national pattern. The National Interagency Fire Center recorded 58,950 wildfires and 10,122,336 acres burned nationwide in 2020, 64,897 fires and 8,924,884 acres in 2024, and 77,850 fires and 5,131,474 acres in 2025. Averaging the ten years from 2016 to 2025 in NIFC's table gives roughly 63,200 fires and about 7.05 million acres a year.

Set California's 2020 total of over 4.2 million acres against that national 2020 figure of just over 10.1 million and the scale becomes clear: in that single year, California accounted for roughly two fifths of all acres burned in the United States.

Which counties dominate any map of California fires?

A map of California fires is not evenly loaded. A small number of counties appear repeatedly on CAL FIRE's Top 20 lists, and once you know which, any map of California fires becomes easier to read at a glance. Acreage concentrates in the far north; destruction concentrates in the North Bay and Southern California.

Counties on the largest-fires list

By our count of CAL FIRE's Top 20 Largest list, Trinity County appears four times, and Butte, Plumas, Shasta, Tehama, Lake and Colusa each appear three times. Mendocino, Glenn, Lassen, Siskiyou, Santa Barbara, Ventura and San Diego each appear twice.

That distribution reflects fuel continuity and terrain. Trinity, Siskiyou and Shasta counties contain vast blocks of steep, roadless mixed conifer. Fires there can burn for weeks without reaching a road, let alone a town, which is why acreage accumulates and structure loss often stays low.

Counties on the most destructive list

The picture inverts on CAL FIRE's Top 20 Most Destructive list. By our count, Sonoma County appears five times, Napa four, Butte three, and Los Angeles, San Diego, Lake, Plumas, Shasta and Ventura twice each.

Sonoma and Napa dominate because Diablo wind events push fire out of the Mayacamas and Sonoma Mountains into valley communities within hours. Los Angeles County entered the top of the list in a single month, January 2025, with Eaton and Palisades destroying 16,246 structures between them.

How to use a county pattern responsibly

Historical frequency is not a forecast, and a map of California fires from last decade will not predict this week. The Camp Fire destroyed Paradise in a county that had never before produced a fire of that consequence, and the Eaton Fire burned in January in a county whose historical entries date from 1933, 1966 and 1968.

Treat the county pattern as a prior, then update it with today's data. The layers that update are the ones that decide: current Red Flag status, current fuel dryness, current wind forecast and the location of live detections. A short daily check of those four live layers beats any amount of historical pattern-matching.

How does a California fire map cover all 58 counties?

California has 58 counties, and a statewide California fire map has to reconcile three overlapping systems across all of them: CAL FIRE units, federal land units, and county-level evacuation zones. The county notes below give the practical detail for the fifteen counties where fires most often become significant.

Los Angeles County

Los Angeles County is a Local Responsibility Area county for most of its populated area, served by the Los Angeles County Fire Department and the Los Angeles Fire Department in the city. It carries two entries on CAL FIRE's most destructive list, both from January 2025, and five of the twenty deadliest California fires.

The county's fire corridors follow the Santa Monica Mountains, the San Gabriel foothills from Altadena eastward, the Santa Clarita Valley and the Angeles National Forest. Cal OES assigned five state-owned Type-6 engines to the Los Angeles City Fire Department in 2026, forming a strike team for both urban and wildland response.

Ventura County

Ventura County supplies three fires to CAL FIRE's lists: Thomas (December 2017, 281,893 acres with Santa Barbara), Woolsey (November 2018, 96,949 acres and 1,643 structures) and Matilija (September 1932, 220,000 acres). The county sits at the western end of the Transverse Ranges, where Santa Ana flow accelerates through canyon mouths.

Santa Barbara County

Santa Barbara County holds the Zaca Fire (July 2007, 240,207 acres, one structure destroyed) and shares Thomas with Ventura. Its distinctive hazard is terrain-driven downslope wind off the Santa Ynez Mountains, which can push fire from the backcountry to the coastal shelf where nearly all the county's population lives.

San Diego County

San Diego County is a Year-Round CAL FIRE unit and one of only three so listed. It contributes the Cedar Fire (October 2003, 273,246 acres, 2,820 structures, 15 deaths) and the Witch Fire (October 2007, 197,990 acres, 1,650 structures) to the largest and most destructive lists, plus four entries on the deadliest list.

Riverside County

Riverside County is the second of CAL FIRE's Year-Round units. Its hazard spans coastal-influenced chaparral in the west, the San Jacinto and Santa Rosa mountains, and desert transition in the east. On a California fire map, Riverside incidents frequently sit on the boundary between state, federal and tribal responsibility.

San Bernardino County

San Bernardino is the third Year-Round unit and one of the largest counties in the contiguous United States by area. The Old Fire of October 2003 burned 91,281 acres, destroyed 1,003 structures and killed 6 people. The San Bernardino Mountains combine dense conifer, mountain communities and Santa Ana exposure through the Cajon Pass.

Orange County

Orange County gives the Santa Ana wind its name, through the Santa Ana Canyon. It is heavily built out, with fire hazard concentrated in the Santa Ana Mountains, the Cleveland National Forest boundary and the coastal canyons. In early September 2026 the Gibby Fire in Orange County reached 230 acres and 95 percent containment.

Butte County

Butte County appears three times on both CAL FIRE Top 20 lists. It holds the Camp Fire (November 2018, 153,336 acres, 18,804 structures, 85 deaths), the deadliest and most destructive California wildfire on record, plus the North Complex, the Dixie Fire and the Park Fire.

The pattern is consistent: fires start in the Feather River canyon country or the foothills and run west into the mosaic of ridge-top towns. Butte is the clearest example in California of a county where acreage and consequence both run high.

Shasta and Trinity counties

Shasta County holds the Carr Fire (July 2018, 229,651 acres, 1,614 structures, 8 deaths) and the Jones Fire (October 1999, 26,200 acres, 954 structures), and shares the Dixie and Park fires. Trinity County appears in four of the twenty largest California wildfires, more than any other county by our count.

Siskiyou County

Siskiyou County holds the Klamath Theater Complex (June 2008, 192,038 acres, two deaths) and shares the River Complex with Trinity. Its fires are overwhelmingly lightning-driven, and much of the burned area is national forest, so federal incident records matter more than state ones here.

Sonoma, Napa and Lake counties

These three counties are the North Bay core. Sonoma appears in five of CAL FIRE's twenty most destructive fires and Napa in four, by our count. Lake County appears three times on the largest list and twice on the destructive list, reflecting the Mendocino Complex, the LNU Lightning Complex, the August Complex and the Valley Fire.

They are served by the CAL FIRE Sonoma-Lake-Napa Unit, which declared its 2026 summer preparedness on June 1, 2026. The defining hazard is an autumn Diablo wind event on cured chaparral above valley communities.

Mendocino County

Mendocino County appears twice on the largest list, through the August Complex and the Mendocino Complex, and once on the destructive list through the Redwood Valley Fire of October 2017, which destroyed 544 structures and killed 9 people. Coast Range fuel continuity plus inland valleys is the recurring pattern.

El Dorado and the Tahoe counties

El Dorado County shares the Caldor Fire with Alpine and Amador counties: 221,835 acres in August 2021, with just over a thousand structures destroyed. The Caldor Fire is the reference case for a Sierra fire crossing the crest and forcing evacuations on the far side of it.

Monterey County

Monterey County, part of the CAL FIRE San Benito-Monterey Unit which declared on May 18, 2026, held California's two largest active fires in early September 2026: the Plaskett Fire at 29,885 acres and 61 percent containment, and the Timber Fire at 25,380 acres and 27 percent containment.

The other 43 counties

The counties not listed above still burn. Alpine, Amador, Tuolumne, Calaveras, Mariposa, Madera, Fresno, Tulare and Kern all carry Sierra fire exposure; the Creek Fire in Fresno and Madera reached 379,895 acres in 2020. Santa Cruz and San Mateo produced the CZU Lightning Complex and its 1,490 destroyed structures.

Alameda and Contra Costa carry East Bay hills exposure, demonstrated by the Tunnel Fire's 2,900 destroyed structures on 1,600 acres in 1991. Glenn County holds the Rattlesnake Fire of July 1953, which killed 15 people on 1,340 acres and still ranks eighth on CAL FIRE's deadliest list.

A statewide filter is the practical answer to this long tail. US Wildfire Tracker covers all 50 states plus DC, so you can hold the California view and still see a fire in Nevada or Oregon that is sending smoke across the state line.

What do evacuation orders on a CA fire map mean?

California uses standardized evacuation terminology, and the two terms that matter most are Evacuation Order and Evacuation Warning. On a CA fire map they appear as coloured zone polygons, and the official definitions are published in the CAL FIRE map legend.

The official definitions

CAL FIRE defines an Evacuation Order as "An immediate threat to life. This is an order by law enforcement to leave immediately. The area is lawfully closed to public access," in the legend published with its current incidents page. There is no discretion built into that wording, and the closure is enforceable.

CAL FIRE defines an Evacuation Warning as "A potential threat to life and/or property. Those who require additional time to evacuate and those with pets and livestock should leave immediately." A warning is not a suggestion to wait; it is the moment people with horses, mobility needs or multiple vehicles are supposed to go.

Cal OES puts the same distinction in plainer language: an evacuation warning means "impending danger to your life or property," and if a warning is given you should assume an evacuation order will follow. An evacuation order means "there's an immediate threat to your life and you need to leave right now."

Who issues an evacuation order in California

Evacuation orders are issued by law enforcement, typically a county sheriff or a city police department, working with the incident commander. Fire agencies recommend; law enforcement orders and enforces. This is why a California fire map has to carry a county evacuation layer that is separate from the fire incident layer.

Many California counties now divide their territory into pre-drawn evacuation zones with alphanumeric identifiers. Learning your zone identifier before a fire is the single highest-value preparation step, because during an incident the official messaging refers to zones, not to street names.

Road closures and re-entry

Closures follow evacuation zones, and the CAL FIRE map legend carries a matching Evacuation Order Lifted status for re-entry. A "hard closure" means no public access at all; a "soft closure" or resident-only closure means people who can prove residency may pass. Re-entry is granted zone by zone, and CAL FIRE's own wording is that residents "should remain alert for any changes in conditions or updated instructions."

Preparing before the order arrives

1. Find your county evacuation zone identifier now and write it somewhere you will find it under stress.
2. Sign up for your county's emergency alert system; these are the messages that carry zone-level orders.
3. Plan two routes out that do not both use the same canyon road or the same freeway on-ramp.
4. Pack a go bag with medication, documents, phone chargers, water and N95 masks for smoke.
5. Decide in advance where animals go, because livestock and horses are the reason warnings exist.
6. Agree an out-of-area contact so household members can check in when local networks are congested.

How to check fires in California today in 60 seconds

Checking fires in California today should take under a minute if you work in a fixed order. The routine below moves from your own location outward, and it deliberately puts official evacuation status ahead of everything else on the California fire map.

The 60-second routine

1. Seconds 0 to 10: open the map and allow location, or select California from the state filter. Note how many active incidents the state currently shows.
2. Seconds 10 to 20: set a radius appropriate to your province, 10 to 25 miles in Southern California or the North Bay, up to 50 miles in the northern mountains and Sierra.
3. Seconds 20 to 30: check whether any nearby detection carries an official incident record. A named incident with acreage and containment is a confirmed fire; an unlinked heat cluster is not yet.
4. Seconds 30 to 40: read the three timestamps, "Last NIFC update", "Last satellite heat" and "Last GOES heat", and judge how current the picture actually is.
5. Seconds 40 to 50: check for a Red Flag Warning or Fire Weather Watch covering your area, and note the wind direction relative to your position.
6. Seconds 50 to 60: check evacuation status for your zone with your county sheriff or office of emergency services, and act on what it says.

Run that sequence twice a day during a Red Flag period and once a week otherwise. Most of the time it will return nothing, which is the correct outcome. CAL FIRE's own year-to-date figures show 5,294 California wildfires by September 8, 2026 against 317,636 acres, meaning the overwhelming majority stayed small.

What "fires in California today" actually returns

On a typical September day the state map shows a handful of large incidents and a scattering of small ones. On September 10, 2026, CAL FIRE listed the Plaskett Fire at 29,885 acres, the Timber Fire at 25,380 acres, the Gibby Fire at 230 acres, the Steele Fire in Napa County at 45 acres, the Belmont Fire in San Luis Obispo County at 11 acres and the Andressen Fire in Placer County at 1 acre.

That distribution is normal. Two long-running large fires, one nearly contained mid-size fire, and three new starts in the tens of acres or less. Learning to recognise the normal shape of a California fire map makes the abnormal days obvious immediately.

When to escalate from checking to acting

Three conditions together should move you from monitoring to preparing: an active Red Flag Warning, a confirmed incident upwind of you within your chosen radius, and fresh satellite heat within the last hour. Any one alone is common. All three together is the pattern that precedes most California evacuations.

For the location-first version of this routine, including how to interpret smoke without a nearby fire, see our guide to using a fire tracker near me.

How do you set up alerts for a fire in California?

Getting alerted to a fire in California takes three separate systems, not one. Official emergency alerts from your county carry legal orders. Wireless Emergency Alerts reach your phone without a signup. A proximity alert from a fire tracker tells you about new detections before either of those fires.

Official county alerts come first

Every California county operates an emergency notification system, and they are the channel through which evacuation orders reach residents. Cal OES and CAL FIRE consistently direct residents to make an evacuation plan, pack a go bag and sign up for local emergency alerts.

These systems are opt-in for the numbers and addresses you register, so registering a mobile number, a landline and an email address for each address you care about materially improves your coverage. Register the address of an elderly relative as well as your own.

Wireless Emergency Alerts

Wireless Emergency Alerts are pushed to phones in a geographic area by authorised agencies and need no registration. They are broad by design and can cover more area than the actual evacuation zone. Treat a Wireless Emergency Alert as a prompt to check your specific zone, not as the full picture.

Proximity alerts from a fire tracker

US Wildfire Tracker can send proximity notifications for new incidents near you when location is enabled. Location is used only to find nearby fires; it is never stored, sold or shared. Combined with the state filter, that gives you a California-wide picture plus a personal tripwire.

These alerts fire on new detections and new incident records, which means they can arrive before an official evacuation message. That is useful and it is also a responsibility: an early alert is a cue to check the official channels, not a substitute for them.

Setting up the extension in California

The Chrome extension is listed in the Chrome Web Store as Fire Tracker, it is free, no account is required, and it carries no ads or third-party ad trackers. It opens the same map in the Chrome side panel or a full tab, which makes it practical to keep California on screen while you work.

Install it from the Chrome Web Store listing, pin it, grant location if you want proximity features, then set the state filter to California. Our step-by-step setup guide covers pinning, troubleshooting and the side-panel workflow in detail.

How accurate is a live California wildfire map?

A live California wildfire map is accurate about what has been reported and confirmed, and approximate about what is happening right now. No California wildfire map is a real-time camera on the fire line. Understanding which fields are precise, which are lagging and which are probabilistic is the difference between using the map well and misreading it.

What is precise

Incident metadata is precise because it is administrative. The fire name, discovery date, incident type, managing organization and jurisdiction are recorded values. When the map says a fire is managed by a CAL FIRE unit or a national forest, that is a fact, not an estimate.

Acreage and containment are precise as of the moment the incident management team published them. CAL FIRE is explicit that all its incident information "comes from the firelines and must be approved by the Incident Commander in charge of managing the incident prior to release," and that updates cannot be guaranteed on a set schedule.

What lags

Perimeters lag most. They are typically produced once per operational period, often from an overnight infrared flight, so a perimeter can be twelve hours behind a fire that is actively running. During a Santa Ana or Diablo event, that lag is at its worst precisely when accuracy matters most.

Statistics lag too. CAL FIRE notes its year-to-date figures are "Updated weekly from preliminary numbers from our dispatch system and the national Incident Management Situation Report," and that they may change as more accurate information arrives and false alarms are removed. Year-to-date acreage is a moving target, not a ledger.

What is probabilistic

Satellite detections are probabilistic by nature. A thermal anomaly means an instrument measured energy consistent with fire in a pixel, subject to cloud, viewing angle and sensor sensitivity. NOAA's minute-scale geostationary system can flag very small fires, but geostationary resolution is far coarser than polar-orbiting VIIRS.

The four failure modes to expect

First, a false positive: industrial heat, a flare, a prescribed burn or agricultural burning appears as a detection. Second, a false negative: a small or smouldering fire under cloud or dense canopy is missed entirely. Third, a stale record: a fire that is effectively out still shows because the record has not been closed.

Fourth, a jurisdictional gap: a fire on federal land that never appears on a state-only view, or a fire on state land that a federal-only view misses. A fused California wildfire map is the practical answer to that gap. A fused California fire map exists to close that fourth gap, and probability scoring exists to manage the first.

Where the technology is heading

California is investing heavily in detection. ALERTCalifornia, developed by UC San Diego with the state, runs a network of over a thousand cameras, and its AI cameras have detected over 900 fires on state lands before 911 calls were made. The first three FireSat wildfire detection satellites launched in June 2026 from Vandenberg Space Force Base.

Satellite data also drives resource allocation, not just public awareness. Brad Quayle of the US Forest Service Geospatial Technology and Applications Center described the operational use plainly: "We use the satellites to inform decisions on where to stage assets across the country. When there's high competition for firefighters, tankers and aircraft, decisions have to be made on how to distribute those assets."

Honest limitations to hold in mind

No California wildfire map, including this one, is an official emergency service. Satellite detections can lag by minutes to hours and can miss small or smouldering fires under cloud. Official perimeters update on agency schedules that no consumer tool controls. Always follow local evacuation orders over anything a map shows you.

Glossary: what every cal fire map term means

The vocabulary on a cal fire map mixes wildland fire jargon, satellite remote sensing and California-specific administrative terms, and several of the entries below come straight from the CAL FIRE map legend. These definitions use the same wording the issuing agencies use, so they match what you will read on official pages.

Acres burned

Total area inside the fire perimeter, including unburned islands. Reported by the incident management team, not measured by satellite.

Advisory

CAL FIRE map legend status meaning residents should be aware of the situation and be prepared to evacuate if conditions worsen.

Complex

Two or more individual fires managed under a single incident organisation. Seven of California's twenty largest fires are complexes.

Containment

Percentage of the fire's edge with a completed control line around it. Not a measure of how much of the fire is extinguished.

Diablo wind

Per the NWS glossary, winds similar to Santa Anas that occur below canyons in the East Bay hills and can exceed 60 mph in extreme cases.

Evacuation Order

CAL FIRE: an immediate threat to life; an order by law enforcement to leave immediately; the area is lawfully closed to public access.

Evacuation Warning

CAL FIRE: a potential threat to life and/or property; those needing extra time and those with pets and livestock should leave immediately.

Fire Hazard Severity Zone

State Fire Marshal classification of State Responsibility Area land as Moderate, High or Very High hazard, effective April 1, 2024 for SRA.

Fire probability score

US Wildfire Tracker's tier fusing whether an official record is linked, perimeter freshness and satellite heat recency.

Fire Weather Watch

NWS "Be Prepared" alert that upcoming weather could produce extensive wildland fire occurrence or extreme fire behavior.

GOES

NOAA geostationary satellites that generate a fresh image of the contiguous United States every five minutes.

Local Responsibility Area

Land where a city or fire district, rather than the state or a federal agency, holds wildland fire protection responsibility.

MODIS

NASA sensor flown on Terra since 1999 and Aqua since 2002, one of the two core polar-orbiting fire detection instruments.

NIROPS

US Forest Service infrared aircraft program that maps 300,000 acres per hour and can locate a six-inch hotspot from 10,000 feet.

Official perimeter

Mapped polygon of burned area. CAL FIRE notes perimeters are generalized and do not indicate whether structures inside were damaged.

Prescribed fire

Planned, authorised burning. A frequent source of satellite heat detections that are not wildfires.

Red Flag Warning

NWS "Take Action" alert for an ongoing or imminent critical fire weather pattern; national criteria include sustained wind averaging 15 mph or more and relative humidity at or below 25 percent.

Santa Ana wind

Per the NWS glossary, strong, hot, dust-bearing winds descending to the Pacific Coast around Los Angeles from inland desert regions.

Satellite hotspot

A pixel where an instrument measured thermal energy consistent with fire. Not by itself proof of a wildfire.

Shelter in Place

CAL FIRE map legend: go inside the nearest safe building, lock all doors and windows, and stay there until authorities give the all clear.

State Responsibility Area

The over 31 million acres of California wildland where CAL FIRE holds primary fire protection responsibility.

Unit

CAL FIRE's administrative division, usually spanning one to three counties, such as Sonoma-Lake-Napa or Madera-Mariposa-Merced.

VIIRS

Polar-orbiting sensor with a 375-metre imager band, able to detect smaller and cooler fires than MODIS, with nighttime capability.

Weak signal

A detection below 25 percent fire probability, hidden by default on US Wildfire Tracker and toggleable when you want everything.

Two more terms are worth knowing because they change what you should do. "Controlled" means the control line is expected to hold under foreseeable conditions. "Out" means no heat remains. A fire can be 100 percent contained for days before it is declared out, and it will still show heat on satellite during that period.

Frequently Asked Questions About California Fire Map