How long did the River fire last?

It burned between 18 May 2026 and 18 May 2026: 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 1,431 hectares (14.3 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire only entered Kern (1,438 ha, 0.1 %).

What was the weather like?

During the fire the temperature reached 24.3 °C, humidity dropped to 14 % and gusts hit 42 km/h. The fire danger index (FWI) reached 32, 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.

US · United States · 2026-05-18 → 2026-05-18

River Fire, May 2026 Kern

Out · last detection 19 May 2026, 09:53 UTC

The fire started on 18 May 2026 in Kern, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 1,431 hectares, spread across a single county.

It is the 240th largest in California since 2016 (of 442 with a page). Number 221 in United States in 2026, of 423.

Burnt area: 1,431ha; official perimeter (MTBS / NIFC)
Duration: 1day; 18 May 2026 – 18 May 2026
Municipalities hit: 1; counties
Started on: 18 May; 2026
Heat detections: 26; in a single hotspot: 38 MW
Danger at start: 32; High · FWI index
Energy released: 334MW; sum of detected power

Play back 19 May 2026

HOTSPOTS BY DAY 18 May18 May

How it evolved, day by day

1819

Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.

The weather it burned in

24°high

42km/h · peak gust

14%lowest humidity

It had gone 12 days 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

Kern where it started

1,438 ha reached on 18 May

0.1 %

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)
18 May	24.3 °C	14 %	42 km/h	0.0 mm	High 32
19 May after	26.8 °C	9 %	37 km/h	0.0 mm	High 37
20 May after	27.5 °C	13 %	42 km/h	0.0 mm	High 38
21 May after	29.1 °C	17 %	43 km/h	0.0 mm	Very high 39
22 May after	28.9 °C	18 %	42 km/h	0.0 mm	Very high 38
23 May after	29.1 °C	16 %	43 km/h	0.0 mm	Very high 39
24 May after	27.4 °C	23 %	41 km/h	0.0 mm	High 35
25 May after	26.5 °C	31 %	39 km/h	0.0 mm	High 31
26 May after	18.8 °C	36 %	46 km/h	0.0 mm	High 28
27 May after	18.2 °C	28 %	38 km/h	0.4 mm	High 28
28 May after	15.2 °C	42 %	37 km/h	0.6 mm	Moderate 19

Before and after, from space

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

↔

Before · 11 May 2026

After · 25 May 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 17 May 2026 the air beside the fire reached 12 µg/m³ of PM2.5, but no daily average passed the WHO guideline (15).

PM2.5 peak12 µg/m³

Days over the guideline0 days

PM1051 µg/m³

Optical depth0.15

161718192021

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 · 26Every 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 River fire last?: It burned between 18 May 2026 and 18 May 2026: 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 1,431 hectares (14.3 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire only entered Kern (1,438 ha, 0.1 %).
What was the weather like?: During the fire the temperature reached 24.3 °C, humidity dropped to 14 % and gusts hit 42 km/h. The fire danger index (FWI) reached 32, 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

Satellite cross-check

NASA FIRMS ↗
NIFC · Fire maps ↗

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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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