How long did the Bm Hill Fire last?

The official perimeter only gives the start date (7 July 2021). The end comes from the heat detections inside the perimeter: it burned until 31 July 2021 (25 days from 7 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 2,206 hectares (22.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 3 counties: Clearwater (1,522 ha, 0.2 %); Missoula (498 ha, 0.1 %); Idaho (182 ha, 0.0 %).

What was the weather like?

During the fire the temperature reached 35.6 °C, humidity dropped to 8 % and gusts hit 59 km/h. The fire danger index (FWI) reached 52, class 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.

US · United States · 2021-07-07 → 2021-07-31

Bm Hill Fire, July 2021 Clearwater, Missoula, Idaho

Out · last detection 31 Jul 2021, 20:16 UTC

The fire started on 7 July 2021 in Clearwater, United States, and satellites saw it burning for 25 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 2,206 hectares, spread across 3 counties.

It is the 133th largest in Idaho since 2016 (of 379 with a page). Number 156 in United States in 2021, of 385.

Compare with…

Suggestions: Storm Creek · 2021 Lolo Peak · 2017 Warm Springs · 2022 Cedar · 2016

Burnt area: 2,206ha; official perimeter (MTBS / NIFC)
Duration: ≈ 25days; 7 Jul 2021 – 31 Jul 2021
Counties hit: 3; counties
Started on: 7 Jul; 2021
Heat detections: 599; in a single hotspot: 141 MW
Danger at start: 28; High · FWI index
Average daily power: 298MW; detected power per day, on average

HOTSPOTS BY DAY 7 Jul31 Jul

Play back 31 Jul 2021

How it evolved, day by day

9 Jul 11 Jul 13 Jul 17 Jul 22 Jul 26 Jul 30 Jul

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

59km/h · peak gust

8%lowest humidity

It had gone 16 days without rain (1 mm or more) when it started. Rain came after the fire: 15.1 mm on 1 Aug.

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 1.4% of the area of London (22 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

Clearwater where it started

1,522 ha reached on 9 Jul

0.2 %
Missoula

498 ha reached on 11 Jul

0.1 %
Idaho

182 ha reached on 15 Jul

0.0 %

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)
7 Jul	29.2 °C	21 %	59 km/h	1.4 mm	High 28
8 Jul	27.7 °C	16 %	44 km/h	0.0 mm	High 33
9 Jul	28.7 °C	13 %	37 km/h	0.2 mm	High 35
10 Jul	31.0 °C	12 %	48 km/h	0.0 mm	Very high 42
11 Jul	29.6 °C	12 %	48 km/h	0.0 mm	Very high 43
12 Jul	31.9 °C	8 %	30 km/h	0.0 mm	Very high 41
13 Jul	30.0 °C	18 %	33 km/h	0.0 mm	Very high 39
14 Jul	32.1 °C	10 %	35 km/h	0.0 mm	Very high 43
15 Jul	30.2 °C	14 %	50 km/h	0.4 mm	Very high 49
16 Jul	28.3 °C	15 %	45 km/h	0.0 mm	Very high 45
17 Jul	29.7 °C	17 %	42 km/h	0.0 mm	Very high 44
18 Jul	32.0 °C	14 %	43 km/h	0.0 mm	Very high 45
19 Jul	28.8 °C	23 %	40 km/h	0.0 mm	Very high 40
20 Jul	28.7 °C	28 %	35 km/h	0.8 mm	High 25
21 Jul	27.7 °C	23 %	57 km/h	1.4 mm	High 26
22 Jul	25.3 °C	13 %	48 km/h	0.0 mm	Very high 38
23 Jul	26.0 °C	14 %	48 km/h	0.0 mm	Very high 41
24 Jul	30.7 °C	11 %	36 km/h	0.0 mm	Very high 42
25 Jul	31.2 °C	10 %	45 km/h	0.0 mm	Very high 47
26 Jul	32.9 °C	13 %	52 km/h	0.1 mm	Extreme 51
27 Jul	29.8 °C	23 %	37 km/h	0.0 mm	Very high 43
28 Jul	31.1 °C	22 %	29 km/h	0.2 mm	Very high 39
29 Jul	31.8 °C	16 %	31 km/h	0.0 mm	Very high 40
30 Jul	35.6 °C	9 %	30 km/h	0.0 mm	Very high 47
31 Jul	34.4 °C	14 %	46 km/h	0.0 mm	Extreme 52
1 Aug after	30.9 °C	31 %	34 km/h	15.1 mm	Very low 4

Before and after, from space

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

↔

Before · 30 Jun 2021

After · 7 Aug 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 · 599Every 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 Bm Hill Fire last?: The official perimeter only gives the start date (7 July 2021). The end comes from the heat detections inside the perimeter: it burned until 31 July 2021 (25 days from 7 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 2,206 hectares (22.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 3 counties: Clearwater (1,522 ha, 0.2 %); Missoula (498 ha, 0.1 %); Idaho (182 ha, 0.0 %).
What was the weather like?: During the fire the temperature reached 35.6 °C, humidity dropped to 8 % and gusts hit 59 km/h. The fire danger index (FWI) reached 52, class 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

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.

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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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What really happened?

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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. 599 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