How long did the Scalp Fire last?

The official perimeter only gives the start date (16 August 2017). The end comes from the heat detections inside the perimeter: it burned until 13 September 2017 (29 days from 16 August 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 8,230 hectares (82.3 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 3 counties: Flathead (6,508 ha, 0.5 %); Lewis and Clark (1,633 ha, 0.2 %); Teton (45 ha, 0.0 %).

What was the weather like?

During the fire the temperature reached 27.1 °C, humidity dropped to 9 % and gusts hit 66 km/h. The fire danger index (FWI) reached 45, 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 · 2017-08-16 → 2017-09-13

Scalp Fire, August 2017 Flathead, Lewis and Clark, Teton

Out · last detection 13 Sept 2017, 19:45 UTC

The fire started on 16 August 2017 in Flathead, United States, and satellites saw it burning for 29 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 8,230 hectares, spread across 3 counties.

It is the 37th largest in Montana since 2016 (of 302 with a page). Number 99 in United States in 2017, of 619.

Compare with…

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Burnt area: 8,230ha; official perimeter (MTBS / NIFC)
Duration: ≈ 29days; 16 Aug 2017 – 13 Sept 2017
Counties hit: 3; counties
Started on: 16 Aug; 2017
Heat detections: 1,907; in a single hotspot: 492 MW
Danger at start: 21; Moderate · FWI index
Average daily power: 1.5GW; detected power per day, on average

HOTSPOTS BY DAY 16 Aug13 Sept

Play back 13 Sept 2017

How it evolved, day by day

17 Aug 21 Aug 26 Aug 30 Aug 2 Sept 3 Sept 7 Sept 11 Sept

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

The weather it burned in

27°high

66km/h · peak gust

9%lowest humidity

It had gone 2 days without rain (1 mm or more) when it started. Rain came after the fire: 14.9 mm on 14 Sept.

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 5.2% of the area of London (82 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

Flathead where it started

6,508 ha reached on 17 Aug

0.5 %
Lewis and Clark

1,633 ha reached on 1 Sept

0.2 %
Teton

45 ha reached on 7 Sept

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 2015

Built-up area0.17 ha

Residents< 20

Inside the perimeter there were about 0.17 hectares of built-up land and almost nobody lived there (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)
16 Aug	20.4 °C	25 %	45 km/h	0.0 mm	Moderate 21
17 Aug	21.0 °C	25 %	47 km/h	0.1 mm	High 24
18 Aug	22.7 °C	23 %	55 km/h	0.0 mm	High 28
19 Aug	19.6 °C	23 %	55 km/h	0.0 mm	High 28
20 Aug	17.8 °C	26 %	48 km/h	0.0 mm	High 27
21 Aug	21.4 °C	21 %	28 km/h	0.0 mm	High 22
22 Aug	25.6 °C	20 %	23 km/h	0.0 mm	High 24
23 Aug	25.8 °C	18 %	50 km/h	0.0 mm	High 32
24 Aug	19.3 °C	35 %	60 km/h	0.4 mm	High 29
25 Aug	21.0 °C	10 %	47 km/h	0.0 mm	High 35
26 Aug	22.7 °C	16 %	37 km/h	0.0 mm	High 33
27 Aug	26.7 °C	14 %	30 km/h	0.0 mm	High 33
28 Aug	27.1 °C	12 %	26 km/h	0.0 mm	High 33
29 Aug	26.2 °C	16 %	23 km/h	0.0 mm	High 34
30 Aug	25.8 °C	16 %	25 km/h	0.0 mm	High 34
31 Aug	22.7 °C	19 %	63 km/h	0.2 mm	Very high 45
1 Sept	22.6 °C	23 %	60 km/h	0.0 mm	Very high 42
2 Sept	26.2 °C	16 %	56 km/h	0.0 mm	Very high 42
3 Sept	27.0 °C	9 %	49 km/h	0.0 mm	Very high 45
4 Sept	16.5 °C	36 %	49 km/h	0.0 mm	High 31
5 Sept	22.6 °C	19 %	25 km/h	0.0 mm	High 27
6 Sept	24.4 °C	15 %	27 km/h	0.1 mm	High 31
7 Sept	25.7 °C	14 %	30 km/h	0.0 mm	High 35
8 Sept	23.3 °C	16 %	32 km/h	0.2 mm	High 36
9 Sept	23.5 °C	30 %	61 km/h	0.8 mm	High 31
10 Sept	18.6 °C	30 %	64 km/h	0.0 mm	High 32
11 Sept	23.7 °C	13 %	55 km/h	0.0 mm	Very high 41
12 Sept	21.9 °C	16 %	46 km/h	0.0 mm	High 38
13 Sept	16.5 °C	31 %	66 km/h	0.8 mm	High 28
14 Sept after	4.3 °C	89 %	31 km/h	14.9 mm	Very low 0

Before and after, from space

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

↔

Before · 9 Aug 2017

After · 20 Sept 2017

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 · 1,907Every 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 Scalp Fire last?: The official perimeter only gives the start date (16 August 2017). The end comes from the heat detections inside the perimeter: it burned until 13 September 2017 (29 days from 16 August 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 8,230 hectares (82.3 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 3 counties: Flathead (6,508 ha, 0.5 %); Lewis and Clark (1,633 ha, 0.2 %); Teton (45 ha, 0.0 %).
What was the weather like?: During the fire the temperature reached 27.1 °C, humidity dropped to 9 % and gusts hit 66 km/h. The fire danger index (FWI) reached 45, 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

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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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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. 1,907 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