Skip to content
worldfires
US · United States · →

Knob Fire, August 2021 Humboldt

Out · last detection 30 Aug 2021, 20:53 UTC

The fire started on 29 August 2021 in Humboldt, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 1,002 hectares, spread across a single county.

It is the 284th largest in California since 2016 (of 442 with a page). Number 233 in United States in 2021, of 385.

Burnt area
1,002ha
official perimeter (MTBS / NIFC)
Duration
1day
29 Aug 2021 – 29 Aug 2021
Municipalities hit
1
counties
Started on
29 Aug
2021
Heat detections
171
in a single hotspot: 87 MW
Danger at start
26
High · FWI index
Energy released
128MW
sum of detected power

Where it burned

HOTSPOTS BY DAY 29 Aug29 Aug

How it evolved, day by day

30

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

The weather it burned in

27°high
40km/h · peak gust
36%lowest humidity

It had gone 32 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

  1. Humboldt where it started
    1,005 ha reached on 30 Aug
    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)
29 Aug 26.8 °C 37 % 32 km/h 0.0 mm High 26
30 Aug after 24.0 °C 43 % 40 km/h 0.0 mm High 25
31 Aug after 23.3 °C 39 % 40 km/h 0.0 mm High 25
1 Sept after 23.7 °C 37 % 35 km/h 0.0 mm High 24
2 Sept after 22.9 °C 41 % 32 km/h 0.0 mm High 23
3 Sept after 24.6 °C 36 % 31 km/h 0.0 mm High 23
4 Sept after 24.8 °C 37 % 30 km/h 0.0 mm High 23
5 Sept after 26.2 °C 35 % 33 km/h 0.0 mm High 24
6 Sept after 29.7 °C 32 % 26 km/h 0.0 mm High 25
7 Sept after 26.6 °C 35 % 33 km/h 0.0 mm High 26
8 Sept after 23.5 °C 46 % 34 km/h 0.0 mm High 23
9 Sept after 22.8 °C 44 % 35 km/h 0.1 mm High 22
10 Sept after 21.7 °C 58 % 36 km/h 0.0 mm Moderate 19
11 Sept after 23.3 °C 51 % 33 km/h 0.0 mm Moderate 18
12 Sept after 23.4 °C 45 % 38 km/h 0.0 mm Moderate 20
13 Sept after 23.9 °C 46 % 35 km/h 0.0 mm Moderate 20

Before and after, from space

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

Before · 22 Aug 2021
After · 5 Sept 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 · 171Every 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 Knob fire last?
It burned between 29 August 2021 and 29 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 1,002 hectares (10.0 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Humboldt (1,005 ha, 0.1 %).
What was the weather like?
During the fire the temperature reached 26.8 °C, humidity dropped to 36 % and gusts hit 40 km/h. The fire danger index (FWI) reached 26, 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

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.

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.