Skip to content
worldfires
en
US · United States · →

Haypress Fire, July 2021 Trinity, Siskiyou

Out · last detection 17 Oct 2021, 09:31 UTC

The fire started on 31 July 2021 in Trinity, United States, and satellites saw it burning for 79 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 82,709 hectares, spread across 2 counties.

It is the 13th largest in California since 2016 (of 442 with a page). Number 6 in United States in 2021, of 385.

Compare with…

Suggestions: Fox · 2020Red Salmon Complex · 2020Cronan · 2021Helena · 2017

Burnt area
82,709ha
official perimeter (MTBS / NIFC)
Duration
≈ 79days
31 Jul 2021 – 17 Oct 2021
Counties hit
2
counties
Started on
31 Jul
2021
Heat detections
20,381
in a single hotspot: 722 MW
Danger at start
26
High · FWI index
Average daily power
3.7GW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 31 Jul17 Oct
17 Oct 2021

How it evolved, day by day

31 Jul 2021 · 66 MW · 5 1 Aug 2021 · 384 MW · 17 2 Aug 2021 · 7,466 MW · 195 3 Aug 2021 · 2,101 MW · 265 4 Aug 2021 · 10,282 MW · 180 5 Aug 2021 · 5,757 MW · 631 6 Aug 2021 · 2,006 MW · 280 7 Aug 2021 · 2,863 MW · 304 8 Aug 2021 · 1,677 MW · 292 9 Aug 2021 · 1,849 MW · 327 10 Aug 2021 · 6,212 MW · 306 11 Aug 2021 · 1,775 MW · 251 12 Aug 2021 · 5,976 MW · 316 13 Aug 2021 · 1,363 MW · 228 14 Aug 2021 · 639 MW · 115 15 Aug 2021 · 5,562 MW · 332 16 Aug 2021 · 3,999 MW · 349 17 Aug 2021 · 4,008 MW · 475 18 Aug 2021 · 11,020 MW · 738 19 Aug 2021 · 7,522 MW · 753 20 Aug 2021 · 2,098 MW · 690 21 Aug 2021 · 1,511 MW · 372 22 Aug 2021 · 1,829 MW · 272 23 Aug 2021 · 1,761 MW · 309 24 Aug 2021 · 1,742 MW · 271 25 Aug 2021 · 2,242 MW · 317 26 Aug 2021 · 2,764 MW · 390 27 Aug 2021 · 3,723 MW · 404 28 Aug 2021 · 4,004 MW · 546 29 Aug 2021 · 3,952 MW · 444 30 Aug 2021 · 4,404 MW · 704 31 Aug 2021 · 6,586 MW · 709 1 Sept 2021 · 3,651 MW · 413 2 Sept 2021 · 2,066 MW · 406 3 Sept 2021 · 5,397 MW · 415 4 Sept 2021 · 6,213 MW · 555 5 Sept 2021 · 12,234 MW · 641 6 Sept 2021 · 22,826 MW · 929 7 Sept 2021 · 29,742 MW · 1124 8 Sept 2021 · 19,597 MW · 1511 9 Sept 2021 · 13,504 MW · 902 10 Sept 2021 · 43 MW · 7 11 Sept 2021 · 244 MW · 50 12 Sept 2021 · 271 MW · 90 13 Sept 2021 · 1,087 MW · 134 14 Sept 2021 · 1,500 MW · 192 15 Sept 2021 · 1,965 MW · 252 16 Sept 2021 · 2,407 MW · 244 17 Sept 2021 · 4,399 MW · 288 18 Sept 2021 · 323 MW · 141 21 Sept 2021 · 20 MW · 6 22 Sept 2021 · 171 MW · 33 23 Sept 2021 · 153 MW · 24 24 Sept 2021 · 212 MW · 40 25 Sept 2021 · 419 MW · 41 26 Sept 2021 · 237 MW · 71 27 Sept 2021 · 16 MW · 9 2 Oct 2021 · 2 MW · 2 3 Oct 2021 · 5 MW · 2 4 Oct 2021 · 20 MW · 8 5 Oct 2021 · 150 MW · 24 8 Oct 2021 · 11 MW · 2 10 Oct 2021 · 117 MW · 6 11 Oct 2021 · 63 MW · 14 12 Oct 2021 · 36 MW · 8 15 Oct 2021 · 2 MW · 3 16 Oct 2021 · 14 MW · 5 17 Oct 2021 · 5 MW · 2
31 Jul 10 Aug 20 Aug 30 Aug 7 Sept 9 Sept 21 Sept 5 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

29°high
67km/h · peak gust
5%lowest humidity

It had gone 0 days without rain (1 mm or more) when it started. Rain came after the fire: 2.6 mm on 18 Oct.

This area had burned before

0% of the perimeter overlaps earlier fires recorded since 2016: 255 ha in 2020.

How big is it?

10 km
It burned the equivalent of 52% of the area of London (827 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. Trinity where it started
    43,679 ha reached on 2 Aug
    5.2 %
  2. Siskiyou
    39,240 ha reached on 31 Jul
    2.4 %

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 area1.0 ha
Residents≈ 30

Inside the perimeter there were about 1.0 hectares of built-up land and about 30 residents (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 25.0 °C 16 % 37 km/h 0.2 mm High 26
1 Aug 23.9 °C 21 % 36 km/h 0.0 mm High 28
2 Aug 23.8 °C 15 % 43 km/h 0.0 mm High 33
3 Aug 24.9 °C 13 % 35 km/h 0.0 mm High 32
4 Aug 24.6 °C 13 % 39 km/h 0.0 mm High 34
5 Aug 19.3 °C 26 % 42 km/h 0.5 mm High 30
6 Aug 23.5 °C 14 % 28 km/h 0.0 mm High 30
7 Aug 24.0 °C 20 % 44 km/h 0.0 mm High 34
8 Aug 24.2 °C 22 % 38 km/h 0.0 mm High 32
9 Aug 24.7 °C 17 % 30 km/h 0.0 mm High 31
10 Aug 27.2 °C 14 % 30 km/h 0.0 mm High 33
11 Aug 28.1 °C 15 % 36 km/h 0.0 mm High 36
12 Aug 27.9 °C 18 % 32 km/h 0.5 mm High 35
13 Aug 25.3 °C 23 % 32 km/h 0.7 mm High 26
14 Aug 26.6 °C 23 % 37 km/h 0.5 mm High 29
15 Aug 29.2 °C 16 % 40 km/h 0.0 mm High 37
16 Aug 25.0 °C 20 % 47 km/h 0.0 mm Very high 39
17 Aug 19.3 °C 12 % 52 km/h 0.0 mm Very high 40
18 Aug 18.2 °C 20 % 53 km/h 0.0 mm Very high 38
19 Aug 21.8 °C 21 % 46 km/h 0.0 mm High 35
20 Aug 21.8 °C 19 % 43 km/h 0.0 mm High 36
21 Aug 18.6 °C 19 % 37 km/h 0.0 mm High 32
22 Aug 20.3 °C 22 % 40 km/h 0.0 mm High 33
23 Aug 20.1 °C 23 % 36 km/h 0.0 mm High 31
24 Aug 18.9 °C 23 % 37 km/h 0.2 mm High 31
25 Aug 20.0 °C 15 % 37 km/h 0.0 mm High 32
26 Aug 22.0 °C 16 % 37 km/h 0.0 mm High 33
27 Aug 24.5 °C 9 % 32 km/h 0.0 mm High 37
28 Aug 26.6 °C 10 % 25 km/h 0.0 mm Very high 38
29 Aug 25.8 °C 12 % 45 km/h 0.0 mm Very high 43
30 Aug 24.3 °C 11 % 44 km/h 0.0 mm Very high 44
31 Aug 22.1 °C 9 % 35 km/h 0.0 mm Very high 41
1 Sept 20.2 °C 18 % 36 km/h 0.0 mm High 35
2 Sept 19.4 °C 17 % 35 km/h 0.0 mm High 34
3 Sept 21.4 °C 14 % 31 km/h 0.0 mm High 34
4 Sept 23.0 °C 10 % 30 km/h 0.0 mm High 35
5 Sept 24.8 °C 6 % 32 km/h 0.0 mm Very high 39
6 Sept 25.7 °C 5 % 29 km/h 0.0 mm Very high 42
7 Sept 25.1 °C 14 % 48 km/h 0.0 mm Very high 45
8 Sept 24.6 °C 18 % 45 km/h 0.0 mm Very high 43
9 Sept 23.1 °C 20 % 61 km/h 1.0 mm High 28
10 Sept 18.1 °C 28 % 36 km/h 2.9 mm Low 6
11 Sept 20.8 °C 21 % 30 km/h 0.0 mm Moderate 16
12 Sept 21.0 °C 15 % 40 km/h 0.0 mm High 30
13 Sept 22.6 °C 13 % 25 km/h 0.0 mm High 31
14 Sept 24.4 °C 12 % 30 km/h 0.0 mm High 34
15 Sept 22.6 °C 14 % 41 km/h 0.0 mm High 37
16 Sept 19.4 °C 21 % 26 km/h 0.0 mm High 31
17 Sept 19.9 °C 22 % 41 km/h 0.0 mm High 33
18 Sept 8.2 °C 60 % 67 km/h 13.3 mm Very low 0
19 Sept 11.6 °C 30 % 54 km/h 1.8 mm Very low 1
20 Sept 18.4 °C 20 % 41 km/h 0.0 mm Low 7
21 Sept 20.8 °C 15 % 34 km/h 0.0 mm Moderate 19
22 Sept 19.5 °C 17 % 39 km/h 0.0 mm High 25
23 Sept 21.0 °C 14 % 32 km/h 0.0 mm High 27
24 Sept 22.9 °C 17 % 28 km/h 0.0 mm High 26
25 Sept 19.7 °C 20 % 35 km/h 0.0 mm High 28
26 Sept 17.3 °C 19 % 43 km/h 0.0 mm High 29
27 Sept 8.0 °C 61 % 54 km/h 12.6 mm Very low 0
28 Sept 8.0 °C 32 % 36 km/h 0.0 mm Very low 1
29 Sept 14.9 °C 21 % 27 km/h 0.0 mm Very low 4
30 Sept 18.7 °C 20 % 32 km/h 0.0 mm Moderate 12
1 Oct 18.2 °C 20 % 22 km/h 0.1 mm Moderate 16
2 Oct 19.1 °C 18 % 24 km/h 0.0 mm Moderate 18
3 Oct 18.7 °C 19 % 29 km/h 0.0 mm Moderate 20
4 Oct 17.0 °C 16 % 44 km/h 0.0 mm High 23
5 Oct 12.9 °C 22 % 48 km/h 0.0 mm High 23
6 Oct 8.9 °C 33 % 32 km/h 2.1 mm Very low 3
7 Oct 9.0 °C 30 % 27 km/h 0.1 mm Low 6
8 Oct 6.8 °C 36 % 38 km/h 0.6 mm Low 8
9 Oct 11.1 °C 28 % 24 km/h 0.0 mm Low 11
10 Oct 10.6 °C 32 % 51 km/h 0.0 mm Moderate 15
11 Oct 2.7 °C 27 % 65 km/h 0.2 mm Moderate 17
12 Oct 7.2 °C 14 % 37 km/h 0.0 mm Moderate 16
13 Oct 7.5 °C 30 % 37 km/h 0.4 mm Moderate 17
14 Oct 10.7 °C 24 % 28 km/h 0.0 mm Moderate 16
15 Oct 14.5 °C 20 % 24 km/h 0.0 mm Moderate 16
16 Oct 15.5 °C 18 % 27 km/h 0.0 mm Moderate 19
17 Oct 7.1 °C 25 % 64 km/h 9.0 mm Very low 1
18 Oct after 3.0 °C 50 % 43 km/h 2.6 mm Very low 0

Before and after, from space

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

Before · 24 Jul 2021
After · 24 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 · 20,381Every 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 Haypress 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 17 October 2021 (79 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 82,709 hectares (827.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire entered 2 counties: Trinity (43,679 ha, 5.2 %); Siskiyou (39,240 ha, 2.4 %).
What was the weather like?
During the fire the temperature reached 29.2 °C, humidity dropped to 5 % and gusts hit 67 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

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.

Report an error
What do you think is wrong?

We will only use your email to reply about this report. Privacy. This is not an emergency service: if there is a fire now, call 911.

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. 20,381 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.