How long did the Thomas Fire last?

The official perimeter only gives the start date (4 December 2017). The end comes from the heat detections inside the perimeter: it burned until 1 January 2018 (29 days from 4 December 2017), the last day with detections before more than 10 days in a row without any, so it is approximate.

How much area did it burn?

The official perimeter published by United States agencies (MTBS / NIFC) is 114,152 hectares (1,141.5 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 2 counties: Ventura (95,701 ha, 20 %); Santa Barbara (19,140 ha, 2.7 %).

What was the weather like?

During the fire the temperature reached 27.5 °C, humidity dropped to 5 % and gusts hit 53 km/h. The fire danger index (FWI) reached 43, class Very high.

Where does this data come from?

From the official burnt perimeter of United States agencies (MTBS / NIFC, public domain), NASA FIRMS VIIRS hotspots and the administrative boundaries of United States. It is not an official report.

US · United States · 2017-12-04 → 2018-01-01

Thomas Fire, December 2017 Ventura, Santa Barbara

Out · last detection 1 Jan 2018, 09:00 UTC

The fire started on 4 December 2017 in Ventura, United States, and satellites saw it burning for 29 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 114,152 hectares, spread across 2 counties.

It is the 9th largest in California since 2016 (of 442 with a page). Number 3 in United States in 2017, of 619.

Compare with…

Suggestions: Pine · 2016 South · 2023 Maria · 2019

Burnt area: 114,152ha; official perimeter (MTBS / NIFC)
Duration: ≈ 29days; 4 Dec 2017 – 1 Jan 2018
Counties hit: 2; counties
Started on: 4 Dec; 2017
Heat detections: 9,339; in a single hotspot: 2,052 MW
Danger at start: 30; High · FWI index
Average daily power: 12.2GW; detected power per day, on average

HOTSPOTS BY DAY 4 Dec1 Jan

Play back 1 Jan 2018

How it evolved, day by day

5 Dec 9 Dec 13 Dec 17 Dec 21 Dec 25 Dec 1 Jan

Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.

The weather it burned in

28°high

53km/h · peak gust

5%lowest humidity

It had gone 27 days without rain (1 mm or more) when it started. Rain came after the fire: 1.0 mm on 3 Jan.

This area had burned before

No earlier perimeters overlap this fire since 2016, when the satellite record begins.

How big is it?

It burned the equivalent of 72% of the area of London (1,142 km² against 1,583 km²).

London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).

This compares size, not location: both shapes are at the same scale, north up, centred on each other.

What happened to each county

Ventura where it started

95,701 ha reached on 5 Dec

20 %
Santa Barbara

19,140 ha reached on 10 Dec

2.7 %

Burnt area inside each county, from crossing the official perimeter with administrative boundaries. The distance runs from the point marking the centre of each area to the nearest fire: staying a kilometre away does not mean it reached the houses.

People and buildings inside the perimeter

GHSL 2015

Built-up area205 ha

Residents≈ 8,300

Inside the perimeter there were about 205 hectares of built-up land and about 8,300 residents (GHSL 2015, satellite-based estimate).

This is an estimate on 100 m cells, made from satellite imagery and census data: it does not mean that homes burned or that anyone was harmed. The perimeter also contains land that never burned.

Source: Global Human Settlement Layer (GHS-BUILT-S and GHS-POP R2023A), European Commission Joint Research Centre (JRC), © European Union, CC BY 4.0. Sum inside the perimeter computed by WorldFires. human-settlement.emergency.copernicus.eu

The weather day by day

ECMWF ERA5 reanalysis at the fire location, the standard reference for past weather, and the Canadian Fire Weather Index (the same system Copernicus uses), computed by WorldFires from that data. Days after the fire run until the first rain.

Open-Meteo.com (CC BY 4.0) · Copernicus Climate Change Service (ERA5)

Day	High	Min. humidity	Peak gust	Rain	Danger (FWI)
4 Dec	20.2 °C	9 %	53 km/h	0.0 mm	High 30
5 Dec	21.4 °C	5 %	53 km/h	0.0 mm	Very high 40
6 Dec	23.4 °C	11 %	35 km/h	0.0 mm	High 36
7 Dec	25.7 °C	8 %	38 km/h	0.0 mm	High 37
8 Dec	25.4 °C	13 %	28 km/h	0.0 mm	High 36
9 Dec	27.3 °C	8 %	36 km/h	0.0 mm	Very high 38
10 Dec	25.9 °C	7 %	41 km/h	0.0 mm	Very high 41
11 Dec	26.0 °C	9 %	35 km/h	0.0 mm	Very high 38
12 Dec	27.1 °C	5 %	30 km/h	0.0 mm	Very high 42
13 Dec	27.5 °C	11 %	31 km/h	0.0 mm	Very high 43
14 Dec	25.9 °C	13 %	31 km/h	0.0 mm	Very high 39
15 Dec	25.6 °C	11 %	27 km/h	0.0 mm	Very high 40
16 Dec	20.0 °C	24 %	30 km/h	0.0 mm	High 34
17 Dec	21.7 °C	7 %	42 km/h	0.0 mm	Very high 38
18 Dec	22.0 °C	16 %	26 km/h	0.0 mm	High 35
19 Dec	20.3 °C	28 %	25 km/h	0.0 mm	High 28
20 Dec	18.3 °C	35 %	47 km/h	0.0 mm	High 28
21 Dec	16.0 °C	26 %	32 km/h	0.0 mm	High 26
22 Dec	18.6 °C	20 %	22 km/h	0.0 mm	High 25
23 Dec	20.2 °C	17 %	22 km/h	0.0 mm	High 27
24 Dec	22.7 °C	11 %	26 km/h	0.0 mm	High 33
25 Dec	21.0 °C	17 %	24 km/h	0.0 mm	High 33
26 Dec	22.0 °C	30 %	24 km/h	0.0 mm	High 30
27 Dec	24.1 °C	28 %	24 km/h	0.0 mm	High 30
28 Dec	26.0 °C	14 %	24 km/h	0.0 mm	High 34
29 Dec	26.8 °C	14 %	22 km/h	0.0 mm	High 34
30 Dec	23.2 °C	18 %	23 km/h	0.0 mm	High 33
31 Dec	21.4 °C	28 %	27 km/h	0.0 mm	High 30
1 Jan	22.6 °C	26 %	26 km/h	0.0 mm	High 30
2 Jan after	22.9 °C	21 %	26 km/h	0.0 mm	High 30
3 Jan after	21.9 °C	24 %	27 km/h	1.0 mm	High 23

Before and after, from space

Drag the line to compare the same ground before the fire and after it.

↔

Before · 27 Nov 2017

After · 8 Jan 2018

Before After

If the day is cloudy, change the date: each satellite passes once a day. In false colour the burnt ground looks brown or red.

Detections table · 9,339Every satellite heat detection, one by one, with time, satellite, power and coordinates.

⬇ Download CSV Times in UTC. Each detection is a 375 m pixel: a large fire yields hundreds per pass.

Date and time	Satellite	FRP (MW)	Lat	Lon

Other fires nearby

All fires in United States ›

Frequently asked questions

How long did the Thomas Fire last?: The official perimeter only gives the start date (4 December 2017). The end comes from the heat detections inside the perimeter: it burned until 1 January 2018 (29 days from 4 December 2017), the last day with detections before more than 10 days in a row without any, so it is approximate.
How much area did it burn?: The official perimeter published by United States agencies (MTBS / NIFC) is 114,152 hectares (1,141.5 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 2 counties: Ventura (95,701 ha, 20 %); Santa Barbara (19,140 ha, 2.7 %).
What was the weather like?: During the fire the temperature reached 27.5 °C, humidity dropped to 5 % and gusts hit 53 km/h. The fire danger index (FWI) reached 43, class Very high.
Where does this data come from?: From the official burnt perimeter of United States agencies (MTBS / NIFC, public domain), NASA FIRMS VIIRS hotspots and the administrative boundaries of United States. It is not an official report.

Where to verify it

A satellite detection is not an official report. Final figures and the fire’s status are published by each country’s emergency service.

Emergency number: 911 · Emergency number and official warnings ›

Satellite cross-check

NASA FIRMS ↗
NIFC · Fire maps ↗

History of this page Changes in area, dates, name, official record or merged pages, compared every night since 24 October 2026.

No changes since 24 October 2026.

RSS Changes to this page

Does something look wrong on this page?

This page is built from satellite data and official records, and it sometimes gets things wrong: the wrong dates, the wrong town, two fires merged into one, or something that was not a wildfire at all. If you know this fire first-hand (you live nearby, saw it, fought it or reported on it), tell us what really happened and we will check it.

Report an error

What do you think is wrong?

Dates or duration Place or towns Burned area Name It was not a wildfire Same fire as another page Something else

What really happened?

Your connection to the fire (optional) Email (optional)

We will only use your email to reply about this report. Privacy. This is not an emergency service: if there is a fire now, call 911.

How we know this

Perimeter: MTBS (US Geological Survey and US Forest Service), official.
The official perimeter has no end date: the end is the last day with VIIRS detections inside the perimeter before a gap of more than 10 days (150 days at most), so it is approximate. 9,339 Suomi-NPP VIIRS detections on those dates.
We have not matched this page with any official record.
Weather: Copernicus ERA5 reanalysis at the fire location, in cells of about 25 km.
Built-up area and population come from the JRC Global Human Settlement Layer (epoch 2015, 100 m cells), summed inside the perimeter: an estimate of what was there, not a damage count.

How we build fire pages: methodology ›

Where this data comes from

The perimeter is official and in the public domain. For past years it comes from MTBS (Monitoring Trends in Burn Severity), run by the U.S. Geological Survey and the USDA Forest Service, which map it on Landsat and Sentinel-2 imagery. For the current and last year it comes from WFIGS at the National Interagency Fire Center (NIFC): incident perimeters mapped by fire crews, aircraft and imagery. Heat detections come from the VIIRS sensors aboard Suomi-NPP and NOAA-20, distributed by NASA FIRMS at 375 m resolution. County boundaries come from geoBoundaries ADM2 (Public Domain). The area per county is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ slightly from official figures.

Where it burned