How long did the Sinlahekin Fire last?

The official perimeter only gives the start date (26 July 2026). The end comes from the heat detections inside the perimeter: it burned until 2 September 2026 (39 days from 26 July 2026), 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 67,181 hectares (671.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire only entered Okanogan (67,894 ha, 4.9 %).

What was the weather like?

During the fire the temperature reached 28.7 °C, humidity dropped to 13 % and gusts hit 59 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.

US · United States · 2026-07-26 → 2026-09-02

Sinlahekin Fire, July 2026 Okanogan

Out · last detection 2 Sept 2026, 21:14 UTC

The fire started on 26 July 2026 in Okanogan, United States, and satellites saw it burning for 39 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 67,181 hectares, spread across a single county.

It is the 5th largest in Washington since 2016 (of 285 with a page). Number 5 in United States in 2026, of 423.

Compare with…

Suggestions: Palmer · 2020 Chickadee Creek · 2021 Muckamuck · 2021 Okanagan-Similkameen B · 2026

Burnt area: 67,181ha; official perimeter (MTBS / NIFC)
Duration: ≈ 39days; 26 Jul 2026 – 2 Sept 2026
Counties hit: 1; counties
Started on: 26 Jul; 2026
Heat detections: 5,096; in a single hotspot: 460 MW
Danger at start: 34; High · FWI index
Average daily power: 3.1GW; detected power per day, on average

HOTSPOTS BY DAY 26 Jul2 Sept

Play back 2 Sept 2026

How it evolved, day by day

26 Jul 30 Jul 1 Aug 9 Aug 15 Aug 19 Aug 23 Aug 27 Aug

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

59km/h · peak gust

13%lowest humidity

It had gone 25 days without rain (1 mm or more) when it started. Rain came after the fire: 13.7 mm on 3 Sept.

This area had burned before

3% of the perimeter overlaps earlier fires recorded since 2016: 1,471 ha in 2020, 282 ha in 2021.

How big is it?

It burned the equivalent of 42% of the area of London (672 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

Okanogan where it started

67,894 ha reached on 26 Jul

4.9 %

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 2025

Built-up area10 ha

Residents≈ 300

Inside the perimeter there were about 10 hectares of built-up land and about 300 residents (GHSL 2025, 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. The GHSL 2025 epoch is a projection made from 2020 and earlier data.

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)
26 Jul	24.0 °C	20 %	46 km/h	0.0 mm	High 34
27 Jul	23.6 °C	26 %	42 km/h	0.5 mm	High 34
28 Jul	23.9 °C	22 %	47 km/h	0.0 mm	High 34
29 Jul	23.7 °C	23 %	24 km/h	0.0 mm	High 31
30 Jul	25.4 °C	17 %	39 km/h	0.0 mm	High 36
31 Jul	28.1 °C	13 %	38 km/h	0.0 mm	Very high 42
1 Aug	23.7 °C	21 %	58 km/h	0.0 mm	Very high 46
2 Aug	17.5 °C	24 %	41 km/h	0.3 mm	High 35
3 Aug	20.4 °C	25 %	34 km/h	0.0 mm	High 32
4 Aug	22.8 °C	25 %	24 km/h	0.0 mm	High 30
5 Aug	25.9 °C	20 %	35 km/h	0.0 mm	High 34
6 Aug	27.7 °C	16 %	28 km/h	0.0 mm	High 36
7 Aug	28.6 °C	16 %	34 km/h	0.0 mm	High 37
8 Aug	23.9 °C	25 %	25 km/h	0.0 mm	High 35
9 Aug	25.1 °C	21 %	29 km/h	0.0 mm	High 35
10 Aug	25.6 °C	21 %	30 km/h	0.0 mm	High 35
11 Aug	24.8 °C	25 %	24 km/h	0.0 mm	High 34
12 Aug	21.4 °C	31 %	36 km/h	0.9 mm	High 22
13 Aug	19.4 °C	35 %	37 km/h	2.8 mm	Low 7
14 Aug	20.5 °C	33 %	25 km/h	2.0 mm	Low 6
15 Aug	22.0 °C	31 %	29 km/h	0.1 mm	Moderate 14
16 Aug	23.3 °C	27 %	28 km/h	1.2 mm	Moderate 16
17 Aug	24.3 °C	27 %	22 km/h	0.4 mm	High 22
18 Aug	26.5 °C	23 %	26 km/h	0.0 mm	High 28
19 Aug	26.6 °C	27 %	32 km/h	0.0 mm	High 31
20 Aug	27.6 °C	23 %	28 km/h	0.0 mm	High 29
21 Aug	28.7 °C	20 %	29 km/h	0.0 mm	High 33
22 Aug	25.5 °C	24 %	54 km/h	1.2 mm	High 27
23 Aug	19.3 °C	43 %	34 km/h	2.4 mm	Low 6
24 Aug	23.4 °C	29 %	23 km/h	0.0 mm	Moderate 14
25 Aug	26.7 °C	19 %	26 km/h	0.0 mm	High 29
26 Aug	25.3 °C	23 %	40 km/h	0.0 mm	High 31
27 Aug	22.5 °C	21 %	45 km/h	0.0 mm	High 34
28 Aug	21.1 °C	23 %	28 km/h	0.0 mm	High 28
29 Aug	13.5 °C	49 %	28 km/h	9.8 mm	Very low 0
30 Aug	17.3 °C	40 %	21 km/h	0.0 mm	Very low 4
31 Aug	19.0 °C	36 %	35 km/h	0.0 mm	Low 10
1 Sept	21.7 °C	28 %	42 km/h	0.1 mm	Moderate 19
2 Sept	15.4 °C	41 %	59 km/h	3.6 mm	Very low 5
3 Sept after	11.9 °C	57 %	28 km/h	13.7 mm	Very low 0

Before and after, from space

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

↔

Before · 19 Jul 2026

After · 9 Sept 2026

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.

The smoke

CAMS · Copernicus

On 5 August 2026 the air beside the fire reached 686 µg/m³ of PM2.5. That day averaged 337: 22 times the WHO daily guideline (15).

PM2.5 peak686 µg/m³

Days over the guideline13 days

PM10695 µg/m³

Optical depth3.47

WHO 15

242526272829303112345

Good Fair Moderate Poor Very poor Extremely poor

Particles from the Copernicus CAMS model at the centre of the perimeter; these are not measurements in each town. The pale bar is the worst hour, the solid one the daily average.

Open-Meteo.com (CC BY 4.0) · Copernicus Atmosphere Monitoring Service (CAMS)

Detections table · 5,096Every 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 Sinlahekin Fire last?: The official perimeter only gives the start date (26 July 2026). The end comes from the heat detections inside the perimeter: it burned until 2 September 2026 (39 days from 26 July 2026), 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 67,181 hectares (671.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire only entered Okanogan (67,894 ha, 4.9 %).
What was the weather like?: During the fire the temperature reached 28.7 °C, humidity dropped to 13 % and gusts hit 59 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

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

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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What really happened?

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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: NIFC WFIGS (United States), 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. 5,096 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 2025, 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