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Williams Fork Fire, August 2020 Grand

Out · last detection 24 Oct 2020, 09:42 UTC

The fire started on 14 August 2020 in Grand, United States, and satellites saw it burning for 72 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 5,940 hectares, spread across a single county.

It is the 25th largest in Colorado since 2016 (of 167 with a page). Number 93 in United States in 2020, of 441.

Compare with…

Suggestions: Sugarloaf · 2018

Burnt area
5,940ha
official perimeter (MTBS / NIFC)
Duration
≈ 72days
14 Aug 2020 – 24 Oct 2020
Counties hit
1
counties
Started on
14 Aug
2020
Heat detections
1,201
in a single hotspot: 689 MW
Danger at start
27
High · FWI index
Average daily power
519MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 14 Aug24 Oct
24 Oct 2020

How it evolved, day by day

14 Aug 2020 · 338 MW · 4 15 Aug 2020 · 4,440 MW · 111 16 Aug 2020 · 3,929 MW · 204 17 Aug 2020 · 3,537 MW · 101 18 Aug 2020 · 1,911 MW · 80 19 Aug 2020 · 1,322 MW · 88 20 Aug 2020 · 979 MW · 117 21 Aug 2020 · 106 MW · 7 22 Aug 2020 · 884 MW · 63 23 Aug 2020 · 166 MW · 57 24 Aug 2020 · 145 MW · 24 25 Aug 2020 · 484 MW · 23 26 Aug 2020 · 9 MW · 3 27 Aug 2020 · 16 MW · 5 28 Aug 2020 · 10 MW · 8 4 Sept 2020 · 10 MW · 1 5 Sept 2020 · 12 MW · 1 6 Sept 2020 · 307 MW · 13 7 Sept 2020 · 88 MW · 11 8 Sept 2020 · 2 MW · 2 13 Sept 2020 · 9 MW · 1 14 Sept 2020 · 4 MW · 1 18 Sept 2020 · 49 MW · 3 19 Sept 2020 · 4 MW · 3 25 Sept 2020 · 343 MW · 7 26 Sept 2020 · 144 MW · 9 27 Sept 2020 · 49 MW · 16 28 Sept 2020 · 74 MW · 11 29 Sept 2020 · 275 MW · 24 30 Sept 2020 · 1,186 MW · 29 1 Oct 2020 · 151 MW · 41 3 Oct 2020 · 11 MW · 3 4 Oct 2020 · 67 MW · 5 5 Oct 2020 · 34 MW · 10 6 Oct 2020 · 38 MW · 8 7 Oct 2020 · 100 MW · 5 8 Oct 2020 · 35 MW · 12 9 Oct 2020 · 2,165 MW · 25 10 Oct 2020 · 218 MW · 27 11 Oct 2020 · 35 MW · 17 14 Oct 2020 · 1 MW · 1 17 Oct 2020 · 18 MW · 4 20 Oct 2020 · 3 MW · 2 21 Oct 2020 · 14 MW · 2 22 Oct 2020 · 94 MW · 5 24 Oct 2020 · 65 MW · 7
14 Aug 15 Aug 21 Aug 28 Aug 14 Sept 29 Sept 7 Oct 20 Oct

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

The weather it burned in

22°high
98km/h · peak gust
11%lowest humidity

It had gone 14 days without rain (1 mm or more) when it started. Rain came after the fire: 29.2 mm on 25 Oct.

This area had burned before

0% of the perimeter overlaps earlier fires recorded since 2016: 1 ha in 2018.

How big is it?

10 km
It burned the equivalent of 3.8% of the area of London (59 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. Grand where it started
    5,910 ha reached on 14 Aug
    1.2 %

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 area0.17 ha
Residents< 20

Inside the perimeter there were about 0.17 hectares of 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)
14 Aug 20.1 °C 14 % 46 km/h 0.0 mm High 27
15 Aug 21.1 °C 14 % 46 km/h 0.0 mm High 28
16 Aug 21.5 °C 12 % 32 km/h 0.0 mm High 26
17 Aug 22.0 °C 15 % 38 km/h 0.0 mm High 26
18 Aug 21.5 °C 18 % 47 km/h 0.0 mm High 30
19 Aug 19.6 °C 20 % 55 km/h 0.0 mm High 31
20 Aug 20.1 °C 24 % 55 km/h 1.1 mm Moderate 18
21 Aug 20.6 °C 18 % 52 km/h 0.0 mm High 25
22 Aug 22.1 °C 13 % 44 km/h 0.0 mm High 28
23 Aug 20.4 °C 19 % 41 km/h 0.1 mm High 29
24 Aug 19.6 °C 21 % 30 km/h 1.4 mm Moderate 12
25 Aug 20.2 °C 21 % 33 km/h 0.0 mm Moderate 19
26 Aug 19.9 °C 28 % 32 km/h 2.7 mm Very low 5
27 Aug 19.5 °C 27 % 32 km/h 0.0 mm Moderate 12
28 Aug 16.8 °C 30 % 34 km/h 6.7 mm Very low 2
29 Aug 13.1 °C 45 % 44 km/h 2.6 mm Very low 2
30 Aug 16.8 °C 27 % 72 km/h 0.0 mm Low 8
31 Aug 14.2 °C 26 % 72 km/h 1.1 mm Low 10
1 Sept 13.9 °C 27 % 46 km/h 1.7 mm Very low 5
2 Sept 18.1 °C 21 % 49 km/h 0.0 mm Moderate 15
3 Sept 20.1 °C 18 % 45 km/h 0.0 mm Moderate 20
4 Sept 20.3 °C 15 % 40 km/h 0.0 mm High 23
5 Sept 21.7 °C 16 % 52 km/h 0.0 mm High 27
6 Sept 20.2 °C 16 % 55 km/h 0.0 mm High 28
7 Sept 17.5 °C 16 % 63 km/h 0.0 mm High 29
8 Sept 4.5 °C 67 % 94 km/h 15.1 mm Very low 0
9 Sept 3.3 °C 55 % 50 km/h 0.4 mm Very low 0
10 Sept 4.5 °C 52 % 43 km/h 5.8 mm Very low 0
11 Sept 5.8 °C 40 % 74 km/h 0.2 mm Very low 2
12 Sept 12.3 °C 24 % 38 km/h 0.0 mm Very low 3
13 Sept 16.9 °C 16 % 25 km/h 0.0 mm Low 8
14 Sept 17.1 °C 18 % 29 km/h 0.0 mm Moderate 12
15 Sept 16.4 °C 17 % 41 km/h 0.0 mm Moderate 15
16 Sept 14.2 °C 27 % 32 km/h 0.0 mm Moderate 13
17 Sept 16.3 °C 18 % 34 km/h 0.0 mm Moderate 15
18 Sept 15.6 °C 20 % 35 km/h 0.0 mm Moderate 15
19 Sept 14.7 °C 24 % 50 km/h 0.7 mm Moderate 14
20 Sept 14.6 °C 25 % 59 km/h 0.0 mm Moderate 17
21 Sept 15.3 °C 26 % 35 km/h 0.9 mm Low 10
22 Sept 14.9 °C 24 % 36 km/h 0.2 mm Moderate 13
23 Sept 14.1 °C 23 % 47 km/h 0.0 mm Moderate 16
24 Sept 17.2 °C 20 % 41 km/h 0.0 mm Moderate 18
25 Sept 16.2 °C 20 % 57 km/h 0.0 mm Moderate 21
26 Sept 14.6 °C 22 % 82 km/h 0.0 mm High 24
27 Sept 7.7 °C 25 % 75 km/h 0.3 mm High 24
28 Sept 4.9 °C 20 % 44 km/h 0.0 mm Moderate 18
29 Sept 13.4 °C 19 % 47 km/h 0.0 mm Moderate 20
30 Sept 14.0 °C 13 % 49 km/h 0.0 mm High 23
1 Oct 12.0 °C 18 % 45 km/h 0.0 mm High 22
2 Oct 11.1 °C 18 % 62 km/h 0.0 mm High 27
3 Oct 10.6 °C 22 % 49 km/h 0.0 mm High 23
4 Oct 14.2 °C 21 % 48 km/h 0.0 mm High 23
5 Oct 13.0 °C 17 % 55 km/h 0.0 mm High 25
6 Oct 16.0 °C 13 % 40 km/h 0.0 mm High 24
7 Oct 17.1 °C 12 % 27 km/h 0.0 mm High 23
8 Oct 15.4 °C 11 % 44 km/h 0.0 mm High 28
9 Oct 14.7 °C 16 % 39 km/h 0.0 mm High 26
10 Oct 14.0 °C 19 % 46 km/h 0.0 mm High 28
11 Oct 7.3 °C 32 % 98 km/h 7.2 mm Very low 2
12 Oct 6.4 °C 27 % 74 km/h 0.0 mm Very low 5
13 Oct 10.0 °C 24 % 66 km/h 0.0 mm Low 10
14 Oct 9.6 °C 25 % 98 km/h 0.0 mm Moderate 20
15 Oct 2.5 °C 24 % 73 km/h 0.0 mm Moderate 16
16 Oct 6.6 °C 26 % 74 km/h 0.0 mm Moderate 17
17 Oct 6.8 °C 32 % 82 km/h 0.0 mm Moderate 18
18 Oct 6.5 °C 42 % 81 km/h 0.0 mm Moderate 18
19 Oct 7.4 °C 32 % 70 km/h 0.0 mm Moderate 16
20 Oct 7.3 °C 30 % 68 km/h 0.0 mm Moderate 16
21 Oct 10.7 °C 20 % 69 km/h 0.0 mm Moderate 20
22 Oct 7.5 °C 28 % 73 km/h 0.0 mm Moderate 20
23 Oct 2.5 °C 32 % 59 km/h 0.0 mm Moderate 16
24 Oct 4.2 °C 31 % 85 km/h 0.0 mm Moderate 20
25 Oct after -0.4 °C 46 % 66 km/h 29.2 mm Very low 0

Before and after, from space

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

Before · 7 Aug 2020
After · 31 Oct 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.

Detections table · 1,201Every 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 timeSatelliteFRP (MW)LatLon

Other fires nearby

All fires in United States ›

Frequently asked questions

How long did the Williams Fork Fire last?
The official perimeter only gives the start date (14 August 2020). The end comes from the heat detections inside the perimeter: it burned until 24 October 2020 (72 days from 14 August 2020), 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 5,940 hectares (59.4 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Grand (5,910 ha, 1.2 %).
What was the weather like?
During the fire the temperature reached 22.1 °C, humidity dropped to 11 % and gusts hit 98 km/h. The fire danger index (FWI) reached 31, class 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

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.
  • 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. 1,201 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.