West Fork Fire, July 2023 Idaho
The fire started on 18 July 2023 in Idaho, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 405 hectares, spread across a single county.
It is the 377th largest in Idaho since 2016 (of 379 with a page). Number 305 in United States in 2023, of 305.
Compare with…
We have the official perimeter (MTBS / NIFC) for this fire, but the VIIRS sensors did not capture it in enough detail: no day-by-day evolution, but the split by county is there.
- Burnt area
- 405ha
- official perimeter (MTBS / NIFC)
- Duration
- 1day
- 18 Jul 2023 – 18 Jul 2023
- Counties hit
- 1
- counties
- Started on
- 18 Jul
- 2023
- Danger at start
- 23
- High · FWI index
Where it burned
The weather it burned in
It had gone 7 days without rain (1 mm or more) when it started. Rain came after the fire: 1.1 mm on 24 Jul.
This area had burned before
No earlier perimeters overlap this fire since 2016, when the satellite record begins.
What happened to each county
-
Idaho where it started405 ha0.0 %
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 2025Inside the perimeter there was no noticeable built-up land and almost nobody lived there (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) |
|---|---|---|---|---|---|
| 18 Jul | 25.6 °C | 24 % | 38 km/h | 0.0 mm | High 23 |
| 19 Jul after | 30.8 °C | 15 % | 22 km/h | 0.0 mm | High 24 |
| 20 Jul after | 33.1 °C | 14 % | 38 km/h | 0.0 mm | High 31 |
| 21 Jul after | 33.6 °C | 16 % | 38 km/h | 0.0 mm | High 31 |
| 22 Jul after | 32.2 °C | 19 % | 43 km/h | 0.0 mm | High 34 |
| 23 Jul after | 35.5 °C | 12 % | 34 km/h | 0.0 mm | High 34 |
| 24 Jul after | 31.0 °C | 26 % | 50 km/h | 1.1 mm | High 26 |
Before and after, from space
Drag the line to compare the same ground before the fire and after it.
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 · CopernicusOn 21 July 2023 the air beside the fire reached 10 µg/m³ of PM2.5, but no daily average passed the WHO guideline (15).
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)
Other fires nearby
- 2,340 haWarm Springs IdahoAugust 2022 · 16 days · 19 km away
- 2,206 haBm Hill ClearwaterJuly 2021 · 25 days · 30 km away
- 6,630 haStorm Creek IdahoJuly 2021 · 42 days · 37 km away
- 3,720 haMoose IdahoAugust 2016 · 18 days · 38 km away
- 2,360 haMoose Mountain ClearwaterJuly 2026 · 8 days · 38 km away
- 5,400 haHidden IdahoJuly 2017 · 6 days · 40 km away
Frequently asked questions
- How long did the West Fork Fire last?
- It burned between 18 July 2023 and 18 July 2023: 1 day, according to the start date recorded by United States agencies (MTBS / NIFC) and the heat detections seen by satellite.
- How much area did it burn?
- The official perimeter published by United States agencies (MTBS / NIFC) is 405 hectares (4.0 km²). Other tallies, such as daily incident reports, may give slightly different figures.
- Which counties burned?
- The fire only entered Idaho (405 ha, 0.0 %).
- What was the weather like?
- During the fire the temperature reached 25.6 °C, humidity dropped to 24 % and gusts hit 38 km/h. The fire danger index (FWI) reached 23, 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 ›
- NIFC · National Interagency Fire Center ↗
- InciWeb · Incident Information System ↗
- MTBS · Monitoring Trends in Burn Severity ↗
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.
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
How we know this
- Perimeter: MTBS (US Geological Survey and US Forest Service), official.
- Dates from the perimeter: the VIIRS detections inside it did not change them. No 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.
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.