River Fire, August 2021 Nevada, Placer
The fire started on 4 August 2021 in Nevada, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 1,095 hectares, spread across 2 counties.
It is the 272th largest in California since 2016 (of 442 with a page). Number 218 in United States in 2021, of 385.
The power measured by the satellite is low (3.0 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
- Burnt area
- 1,095ha
- official perimeter (MTBS / NIFC)
- Duration
- 1day
- 4 Aug 2021 – 4 Aug 2021
- Municipalities hit
- 2
- counties
- Started on
- 4 Aug
- 2021
- Heat detections
- 47
- in a single hotspot: 3 MW
- Danger at start
- 48
- Very high · FWI index
- Energy released
- 67MW
- sum of detected power
Where it burned
How it evolved, day by day
Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.
The weather it burned in
It had gone more than two months without rain (1 mm or more) when it started.
This area had burned before
No earlier perimeters overlap this fire since 2016, when the satellite record begins.
What happened to each town
-
Nevada where it started718 ha reached on 5 Aug0.3 %
-
371 ha reached on 5 Aug0.1 %
Burnt area inside each county, from crossing the official perimeter with administrative boundaries. The distance is from the town centre to the nearest fire: staying a kilometre away does not mean it reached the houses.
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) |
|---|---|---|---|---|---|
| 4 Aug | 35.0 °C | 16 % | 36 km/h | 0.0 mm | Very high 48 |
| 5 Aug after | 30.1 °C | 20 % | 36 km/h | 0.0 mm | Very high 44 |
| 6 Aug after | 33.3 °C | 15 % | 37 km/h | 0.0 mm | Very high 46 |
| 7 Aug after | 33.2 °C | 21 % | 33 km/h | 0.0 mm | Very high 43 |
| 8 Aug after | 33.4 °C | 19 % | 36 km/h | 0.0 mm | Very high 45 |
| 9 Aug after | 34.0 °C | 20 % | 33 km/h | 0.0 mm | Very high 44 |
| 10 Aug after | 35.6 °C | 18 % | 33 km/h | 0.0 mm | Very high 44 |
| 11 Aug after | 36.6 °C | 18 % | 37 km/h | 0.0 mm | Very high 46 |
| 12 Aug after | 34.4 °C | 25 % | 36 km/h | 0.0 mm | Very high 43 |
| 13 Aug after | 33.9 °C | 25 % | 33 km/h | 0.0 mm | Very high 39 |
| 14 Aug after | 35.8 °C | 24 % | 34 km/h | 0.0 mm | Very high 42 |
| 15 Aug after | 36.1 °C | 27 % | 32 km/h | 0.0 mm | Very high 41 |
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.
Detections table · 47Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
Frequently asked questions
- How long did the River fire last?
- It burned between 4 August 2021 and 4 August 2021: 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 1,095 hectares (11.0 km²). Other tallies, such as daily incident reports, may give slightly different figures.
- Which counties burned?
- The fire entered 2 counties: Nevada (718 ha, 0.3 %); Placer (371 ha, 0.1 %).
- What was the weather like?
- During the fire the temperature reached 35.0 °C, humidity dropped to 16 % and gusts hit 36 km/h. The fire danger index (FWI) reached 48, 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
- NIFC · National Interagency Fire Center ↗
- InciWeb · Incident Information System ↗
- MTBS · Monitoring Trends in Burn Severity ↗
Satellite cross-check
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
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.