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Tiltill Fire, July 2021 Tuolumne

Out · last detection 30 Sept 2021, 09:50 UTC

The fire started on 31 July 2021 in Tuolumne, United States, and satellites saw it burning for 62 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 1,145 hectares, spread across a single county.

It is the 267th largest in California since 2016 (of 442 with a page). Number 209 in United States in 2021, of 385.

Compare with…

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Burnt area
1,145ha
official perimeter (MTBS / NIFC)
Duration
≈ 62days
31 Jul 2021 – 30 Sept 2021
Counties hit
1
counties
Started on
31 Jul
2021
Heat detections
532
in a single hotspot: 149 MW
Danger at start
13
Moderate · FWI index
Average daily power
119MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 31 Jul30 Sept
30 Sept 2021

How it evolved, day by day

1 Aug 2021 · 17 MW · 1 2 Aug 2021 · 228 MW · 5 3 Aug 2021 · 26 MW · 6 4 Aug 2021 · 1,000 MW · 15 5 Aug 2021 · 1,896 MW · 82 6 Aug 2021 · 745 MW · 46 7 Aug 2021 · 546 MW · 57 8 Aug 2021 · 245 MW · 36 9 Aug 2021 · 131 MW · 20 10 Aug 2021 · 212 MW · 27 11 Aug 2021 · 115 MW · 25 12 Aug 2021 · 64 MW · 13 13 Aug 2021 · 33 MW · 8 14 Aug 2021 · 43 MW · 5 15 Aug 2021 · 12 MW · 4 16 Aug 2021 · 3 MW · 3 17 Aug 2021 · 15 MW · 3 18 Aug 2021 · 32 MW · 10 19 Aug 2021 · 20 MW · 8 20 Aug 2021 · 3 MW · 2 22 Aug 2021 · 1 MW · 1 23 Aug 2021 · 2 MW · 1 24 Aug 2021 · 3 MW · 2 25 Aug 2021 · 2 MW · 2 26 Aug 2021 · 1 MW · 1 27 Aug 2021 · 3 MW · 1 28 Aug 2021 · 10 MW · 7 29 Aug 2021 · 80 MW · 7 30 Aug 2021 · 23 MW · 7 31 Aug 2021 · 25 MW · 5 1 Sept 2021 · 6 MW · 5 2 Sept 2021 · 8 MW · 3 3 Sept 2021 · 11 MW · 4 4 Sept 2021 · 57 MW · 7 5 Sept 2021 · 50 MW · 16 6 Sept 2021 · 77 MW · 10 7 Sept 2021 · 84 MW · 10 8 Sept 2021 · 282 MW · 17 9 Sept 2021 · 38 MW · 10 10 Sept 2021 · 3 MW · 4 12 Sept 2021 · 1 MW · 1 13 Sept 2021 · 21 MW · 4 14 Sept 2021 · 43 MW · 7 15 Sept 2021 · 49 MW · 10 16 Sept 2021 · 12 MW · 4 17 Sept 2021 · 6 MW · 2 20 Sept 2021 · 4 MW · 1 21 Sept 2021 · 1 MW · 1 24 Sept 2021 · 1 MW · 1 25 Sept 2021 · 2 MW · 1 26 Sept 2021 · 1 MW · 1 27 Sept 2021 · 2 MW · 2 30 Sept 2021 · 1 MW · 1
1 Aug 5 Aug 9 Aug 17 Aug 26 Aug 3 Sept 12 Sept 24 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
73km/h · peak gust
11%lowest humidity

It had gone one day without rain (1 mm or more) when it started. Rain came after the fire: 1.7 mm on 6 Oct.

This area had burned before

No earlier perimeters overlap this fire since 2016, when the satellite record begins.

How big is it?

10 km
It burned the equivalent of 0.7% of the area of London (11 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. Tuolumne where it started
    1,147 ha reached on 1 Aug
    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 21.0 °C 32 % 38 km/h 0.7 mm Moderate 13
1 Aug 22.0 °C 25 % 44 km/h 0.8 mm Moderate 17
2 Aug 23.4 °C 23 % 44 km/h 0.0 mm High 23
3 Aug 25.1 °C 20 % 42 km/h 0.0 mm High 26
4 Aug 25.1 °C 19 % 48 km/h 0.0 mm High 29
5 Aug 21.0 °C 17 % 60 km/h 0.0 mm High 33
6 Aug 21.2 °C 14 % 38 km/h 0.0 mm High 28
7 Aug 22.7 °C 25 % 44 km/h 0.0 mm High 30
8 Aug 22.7 °C 18 % 45 km/h 0.0 mm High 31
9 Aug 23.6 °C 20 % 46 km/h 0.0 mm High 32
10 Aug 24.1 °C 20 % 35 km/h 0.5 mm High 30
11 Aug 24.6 °C 19 % 36 km/h 1.1 mm High 23
12 Aug 23.9 °C 20 % 40 km/h 0.0 mm High 28
13 Aug 24.7 °C 20 % 35 km/h 0.0 mm High 28
14 Aug 25.2 °C 23 % 34 km/h 0.3 mm High 30
15 Aug 26.5 °C 20 % 30 km/h 0.0 mm High 30
16 Aug 26.1 °C 21 % 42 km/h 0.0 mm High 34
17 Aug 21.9 °C 19 % 58 km/h 0.0 mm High 38
18 Aug 15.9 °C 38 % 50 km/h 0.0 mm High 28
19 Aug 17.7 °C 29 % 38 km/h 0.0 mm High 26
20 Aug 18.6 °C 31 % 46 km/h 0.0 mm High 28
21 Aug 16.2 °C 37 % 56 km/h 0.0 mm High 29
22 Aug 19.1 °C 29 % 45 km/h 0.0 mm High 26
23 Aug 19.1 °C 28 % 47 km/h 0.0 mm High 27
24 Aug 19.4 °C 23 % 48 km/h 0.0 mm High 30
25 Aug 19.5 °C 19 % 48 km/h 0.0 mm High 32
26 Aug 22.5 °C 15 % 40 km/h 0.0 mm High 34
27 Aug 23.7 °C 13 % 45 km/h 0.0 mm Very high 39
28 Aug 24.8 °C 13 % 45 km/h 0.0 mm Very high 41
29 Aug 25.1 °C 13 % 45 km/h 0.0 mm Very high 41
30 Aug 25.0 °C 14 % 49 km/h 0.0 mm Very high 43
31 Aug 22.6 °C 11 % 50 km/h 0.0 mm Very high 44
1 Sept 19.2 °C 15 % 48 km/h 0.0 mm Very high 42
2 Sept 18.4 °C 18 % 45 km/h 0.0 mm Very high 40
3 Sept 20.4 °C 21 % 40 km/h 0.0 mm High 37
4 Sept 23.2 °C 16 % 39 km/h 0.0 mm High 37
5 Sept 25.1 °C 11 % 39 km/h 0.0 mm Very high 40
6 Sept 25.9 °C 13 % 42 km/h 0.0 mm Very high 43
7 Sept 26.8 °C 14 % 44 km/h 0.0 mm Very high 43
8 Sept 26.7 °C 14 % 48 km/h 0.0 mm Very high 46
9 Sept 23.6 °C 18 % 56 km/h 0.0 mm Very high 46
10 Sept 18.3 °C 42 % 73 km/h 2.1 mm Moderate 12
11 Sept 20.1 °C 31 % 43 km/h 0.0 mm Moderate 20
12 Sept 21.8 °C 16 % 46 km/h 0.0 mm High 33
13 Sept 21.3 °C 14 % 45 km/h 0.0 mm High 37
14 Sept 22.9 °C 18 % 41 km/h 0.0 mm High 35
15 Sept 20.7 °C 21 % 49 km/h 0.0 mm Very high 39
16 Sept 18.5 °C 26 % 43 km/h 0.0 mm High 34
17 Sept 18.4 °C 22 % 50 km/h 0.0 mm High 36
18 Sept 15.7 °C 35 % 58 km/h 0.0 mm High 33
19 Sept 15.3 °C 25 % 46 km/h 0.0 mm High 29
20 Sept 21.4 °C 15 % 36 km/h 0.0 mm High 36
21 Sept 20.9 °C 14 % 42 km/h 0.0 mm High 37
22 Sept 19.3 °C 22 % 49 km/h 0.0 mm Very high 39
23 Sept 21.6 °C 15 % 34 km/h 0.0 mm High 35
24 Sept 21.6 °C 16 % 38 km/h 0.0 mm High 37
25 Sept 19.8 °C 20 % 45 km/h 0.0 mm Very high 38
26 Sept 18.1 °C 25 % 46 km/h 0.0 mm High 36
27 Sept 16.2 °C 23 % 54 km/h 0.0 mm High 38
28 Sept 11.6 °C 38 % 43 km/h 1.0 mm Moderate 15
29 Sept 14.8 °C 11 % 34 km/h 0.0 mm High 28
30 Sept 18.0 °C 11 % 36 km/h 0.0 mm High 36
1 Oct after 17.4 °C 14 % 41 km/h 0.0 mm High 36
2 Oct after 18.6 °C 14 % 38 km/h 0.0 mm High 35
3 Oct after 17.8 °C 13 % 41 km/h 0.0 mm High 37
4 Oct after 16.4 °C 18 % 43 km/h 0.0 mm High 38
5 Oct after 15.0 °C 26 % 46 km/h 0.0 mm High 34
6 Oct after 10.3 °C 43 % 50 km/h 1.7 mm Low 10

Before and after, from space

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

Before · 24 Jul 2021
After · 7 Oct 2021

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 · 532Every 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 Tiltill 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 30 September 2021 (62 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 1,145 hectares (11.4 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Tuolumne (1,147 ha, 0.2 %).
What was the weather like?
During the fire the temperature reached 26.8 °C, humidity dropped to 11 % and gusts hit 73 km/h. The fire danger index (FWI) reached 46, 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

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. 532 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.