How long did the Cronan Fire last?

The official perimeter only gives the start date (31 July 2021). The end comes from the heat detections inside the perimeter: it burned until 28 August 2021 (29 days from 31 July 2021), 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 3,077 hectares (30.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire only entered Siskiyou (3,071 ha, 0.2 %).

What was the weather like?

During the fire the temperature reached 35.7 °C, humidity dropped to 12 % and gusts hit 56 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 · 2021-07-31 → 2021-08-28

Cronan Fire, July 2021 Siskiyou

Out · last detection 28 Aug 2021, 10:08 UTC

The fire started on 31 July 2021 in Siskiyou, United States, and satellites saw it burning for 29 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 3,077 hectares, spread across a single county.

It is the 169th largest in California since 2016 (of 442 with a page). Number 129 in United States in 2021, of 385.

Compare with…

Suggestions: Butler · 2025 Island · 2017 Haypress · 2017 Red Salmon Complex · 2020

Burnt area: 3,077ha; official perimeter (MTBS / NIFC)
Duration: ≈ 29days; 31 Jul 2021 – 28 Aug 2021
Counties hit: 1; counties
Started on: 31 Jul; 2021
Heat detections: 622; in a single hotspot: 99 MW
Danger at start: 30; High · FWI index
Average daily power: 194MW; detected power per day, on average

HOTSPOTS BY DAY 31 Jul28 Aug

Play back 28 Aug 2021

How it evolved, day by day

31 Jul 4 Aug 8 Aug 12 Aug 16 Aug 19 Aug 20 Aug 24 Aug

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

The weather it burned in

36°high

56km/h · peak gust

12%lowest humidity

It had gone 0 days without rain (1 mm or more) when it started.

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 1.9% of the area of London (31 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

Siskiyou where it started

3,071 ha reached on 31 Jul

0.2 %

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 2020

Built-up area< 0.1 ha

Residents< 20

Inside the perimeter there was no noticeable built-up land and almost nobody lived there (GHSL 2020, 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)
31 Jul	32.1 °C	19 %	41 km/h	0.0 mm	High 30
1 Aug	31.4 °C	24 %	39 km/h	0.0 mm	High 30
2 Aug	30.9 °C	21 %	39 km/h	0.0 mm	High 30
3 Aug	32.2 °C	17 %	38 km/h	0.0 mm	High 34
4 Aug	32.0 °C	17 %	41 km/h	0.0 mm	High 36
5 Aug	26.5 °C	31 %	41 km/h	0.9 mm	High 22
6 Aug	30.3 °C	18 %	36 km/h	0.0 mm	High 32
7 Aug	30.8 °C	26 %	45 km/h	0.0 mm	High 35
8 Aug	30.9 °C	25 %	40 km/h	0.0 mm	High 34
9 Aug	32.5 °C	21 %	32 km/h	0.0 mm	High 33
10 Aug	35.1 °C	18 %	30 km/h	0.0 mm	High 37
11 Aug	35.6 °C	17 %	41 km/h	0.0 mm	Very high 40
12 Aug	35.0 °C	20 %	34 km/h	0.0 mm	Very high 39
13 Aug	32.5 °C	26 %	37 km/h	1.5 mm	High 23
14 Aug	33.5 °C	28 %	40 km/h	0.8 mm	High 28
15 Aug	35.7 °C	22 %	39 km/h	0.0 mm	High 36
16 Aug	30.6 °C	27 %	46 km/h	0.0 mm	High 38
17 Aug	26.2 °C	15 %	50 km/h	0.0 mm	Very high 40
18 Aug	25.4 °C	26 %	56 km/h	0.0 mm	Very high 38
19 Aug	29.1 °C	24 %	49 km/h	0.0 mm	High 36
20 Aug	29.1 °C	20 %	43 km/h	0.0 mm	High 36
21 Aug	25.5 °C	23 %	40 km/h	0.0 mm	High 35
22 Aug	27.4 °C	22 %	42 km/h	0.0 mm	High 37
23 Aug	27.8 °C	22 %	37 km/h	0.0 mm	High 36
24 Aug	26.1 °C	27 %	39 km/h	0.3 mm	High 34
25 Aug	27.0 °C	16 %	39 km/h	0.0 mm	High 38
26 Aug	28.5 °C	21 %	40 km/h	0.0 mm	High 38
27 Aug	31.4 °C	12 %	34 km/h	0.0 mm	Very high 40
28 Aug	34.2 °C	12 %	24 km/h	0.0 mm	Very high 43
29 Aug after	32.6 °C	16 %	45 km/h	0.0 mm	Very high 47
30 Aug after	30.4 °C	16 %	44 km/h	0.0 mm	Very high 47
31 Aug after	28.7 °C	12 %	37 km/h	0.0 mm	Very high 45
1 Sept after	28.1 °C	20 %	36 km/h	0.0 mm	Very high 41
2 Sept after	26.8 °C	16 %	37 km/h	0.0 mm	Very high 40
3 Sept after	28.8 °C	17 %	35 km/h	0.0 mm	Very high 40
4 Sept after	30.3 °C	14 %	32 km/h	0.0 mm	Very high 40
5 Sept after	31.8 °C	11 %	36 km/h	0.0 mm	Very high 43
6 Sept after	33.8 °C	10 %	30 km/h	0.0 mm	Very high 42
7 Sept after	31.7 °C	18 %	49 km/h	0.1 mm	Very high 47

Before and after, from space

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

↔

Before · 24 Jul 2021

After · 4 Sept 2021

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 · 622Every 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 Cronan Fire last?: The official perimeter only gives the start date (31 July 2021). The end comes from the heat detections inside the perimeter: it burned until 28 August 2021 (29 days from 31 July 2021), 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 3,077 hectares (30.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire only entered Siskiyou (3,071 ha, 0.2 %).
What was the weather like?: During the fire the temperature reached 35.7 °C, humidity dropped to 12 % and gusts hit 56 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. 622 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 2020, 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