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Mullins Fire, August 2020 Custer

Out · last measured on 3 Sept 2020

The fire started on 5 August 2020 in Custer, United States, and satellites saw it burning for 30 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 591 hectares, spread across a single county.

It is the 242th largest in Montana since 2016 (of 302 with a page). Number 370 in United States in 2020, of 441.

Compare with…

Suggestions: Sartin Draw · 2017Ranch · 2021Snider · 2020Zook · 2020

We have the official perimeter (MTBS / NIFC) for this fire, but the VIIRS sensors did not capture it in enough detail: no day-by-day evolution, but the split by county is there.

Burnt area
591ha
official perimeter (MTBS / NIFC)
Duration
30days
5 Aug 2020 – 3 Sept 2020
Counties hit
1
counties
Started on
5 Aug
2020
Danger at start
39
Very high · FWI index

Where it burned

The weather it burned in

37°high
75km/h · peak gust
9%lowest humidity

It had gone 4 days without rain (1 mm or more) when it started. Rain came after the fire: 12.7 mm on 7 Sept.

This area had burned before

100% of the perimeter overlaps earlier fires recorded since 2016: 593 ha in 2017.

How big is it?

10 km
It burned the equivalent of 0.4% of the area of London (5.9 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

  1. Custer where it started
    588 ha
    0.1 %

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)
5 Aug 31.0 °C 23 % 35 km/h 0.0 mm Very high 39
6 Aug 34.3 °C 19 % 44 km/h 2.1 mm High 34
7 Aug 30.4 °C 26 % 56 km/h 0.0 mm Very high 42
8 Aug 32.7 °C 18 % 29 km/h 0.0 mm High 36
9 Aug 26.5 °C 21 % 45 km/h 0.0 mm Very high 48
10 Aug 31.5 °C 12 % 34 km/h 0.0 mm Very high 48
11 Aug 33.7 °C 17 % 35 km/h 1.2 mm Very high 43
12 Aug 37.4 °C 9 % 32 km/h 0.3 mm Extreme 54
13 Aug 29.6 °C 21 % 43 km/h 2.4 mm High 34
14 Aug 26.5 °C 22 % 51 km/h 10.6 mm Low 8
15 Aug 31.4 °C 16 % 27 km/h 0.0 mm High 27
16 Aug 33.3 °C 18 % 27 km/h 0.0 mm High 35
17 Aug 37.2 °C 11 % 37 km/h 0.0 mm Extreme 50
18 Aug 35.9 °C 10 % 35 km/h 0.0 mm Very high 49
19 Aug 35.0 °C 17 % 24 km/h 0.0 mm Very high 42
20 Aug 34.5 °C 16 % 23 km/h 0.0 mm Very high 44
21 Aug 32.3 °C 19 % 35 km/h 0.0 mm Very high 43
22 Aug 37.2 °C 10 % 34 km/h 0.0 mm Very high 48
23 Aug 31.0 °C 26 % 36 km/h 0.0 mm Very high 43
24 Aug 35.5 °C 15 % 38 km/h 0.0 mm Very high 49
25 Aug 34.0 °C 20 % 35 km/h 0.0 mm Very high 50
26 Aug 31.8 °C 24 % 26 km/h 0.1 mm High 38
27 Aug 28.7 °C 35 % 40 km/h 0.2 mm Very high 39
28 Aug 25.5 °C 22 % 42 km/h 0.0 mm Very high 43
29 Aug 34.1 °C 13 % 38 km/h 0.0 mm Extreme 51
30 Aug 21.6 °C 31 % 52 km/h 0.6 mm Very high 44
31 Aug 21.4 °C 17 % 27 km/h 0.0 mm High 35
1 Sept 28.2 °C 18 % 59 km/h 0.0 mm Extreme 60
2 Sept 33.3 °C 12 % 75 km/h 0.0 mm Very extreme 93
3 Sept 26.3 °C 22 % 34 km/h 0.0 mm Very high 43
4 Sept after 30.5 °C 18 % 25 km/h 0.0 mm Very high 39
5 Sept after 37.1 °C 10 % 28 km/h 0.0 mm Extreme 52
6 Sept after 26.3 °C 24 % 39 km/h 0.0 mm Extreme 50
7 Sept after 14.7 °C 52 % 48 km/h 12.7 mm Very low 2

Before and after, from space

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

Before · 29 Jul 2020
After · 10 Sept 2020

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

Other fires nearby

All fires in United States ›

Frequently asked questions

How long did the Mullins Fire last?
According to the heat detections seen by satellite inside the perimeter, it burned from 5 August 2020 to 3 September 2020 (30 days). The perimeter dates it from 5 August 2020 to 5 August 2020.
How much area did it burn?
The official perimeter published by United States agencies (MTBS / NIFC) is 591 hectares (5.9 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Custer (588 ha, 0.1 %).
What was the weather like?
During the fire the temperature reached 37.4 °C, humidity dropped to 9 % and gusts hit 75 km/h. The fire danger index (FWI) reached 93, class Very extreme.
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

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.

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How we know this
  • Perimeter: MTBS (US Geological Survey and US Forest Service), official.
  • Dates adjusted with the VIIRS detections inside the perimeter, which said 5 August 2020 to 5 August 2020. No 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.