How long did the Cedar Top Fire last?

The official perimeter only gives the start date (9 August 2023). The end comes from the heat detections inside the perimeter: it burned until 10 August 2023 (2 days from 9 August 2023), 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 935 hectares (9.4 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 2 counties: Knox (893 ha, 0.4 %); Baylor (41 ha, 0.0 %).

What was the weather like?

During the fire the temperature reached 43.0 °C, humidity dropped to 16 % and gusts hit 54 km/h. The fire danger index (FWI) reached 76, class Very extreme.

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 · 2023-08-09 → 2023-08-10

Cedar Top Fire, August 2023 Knox, Baylor

Out · last detection 10 Aug 2023, 07:39 UTC

The fire started on 9 August 2023 in Knox, United States, and satellites saw it burning for 2 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 935 hectares, spread across 2 counties.

It is the 186th largest in Texas since 2016 (of 327 with a page). Number 162 in United States in 2023, of 305.

Compare with…

Suggestions: Coconut · 2022 Waggoner Ranch · 2018 Moonshine · 2023 Santa Rosa Creek · 2023

Burnt area: 935ha; official perimeter (MTBS / NIFC)
Duration: ≈ 2days; 9 Aug 2023 – 10 Aug 2023
Counties hit: 2; counties
Started on: 9 Aug; 2023
Heat detections: 14; in a single hotspot: 147 MW
Danger at start: 76; Very extreme · FWI index
Average daily power: 190MW; detected power per day, on average

HOTSPOTS BY DAY 9 Aug10 Aug

Play back 10 Aug 2023

How it evolved, day by day

9 Aug 10 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

43°high

54km/h · peak gust

16%lowest humidity

It had gone 0 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.

How big is it?

It burned the equivalent of 0.6% of the area of London (9.4 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

Knox where it started

893 ha reached on 9 Aug

0.4 %
Baylor

41 ha

0.0 %

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 2025

Built-up area< 0.1 ha

Residents< 20

Inside 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)
9 Aug	43.0 °C	16 %	54 km/h	0.0 mm	Very extreme 76
10 Aug	40.2 °C	29 %	30 km/h	0.2 mm	Extreme 54
11 Aug after	43.8 °C	16 %	49 km/h	0.0 mm	Very extreme 73
12 Aug after	41.9 °C	24 %	45 km/h	0.4 mm	Very extreme 76
13 Aug after	41.4 °C	22 %	48 km/h	0.0 mm	Extreme 70
14 Aug after	33.1 °C	26 %	51 km/h	0.0 mm	Extreme 62
15 Aug after	34.9 °C	22 %	25 km/h	0.0 mm	Very high 43
16 Aug after	39.4 °C	21 %	33 km/h	0.0 mm	Extreme 54
17 Aug after	44.1 °C	14 %	37 km/h	0.0 mm	Extreme 67
18 Aug after	43.0 °C	14 %	30 km/h	0.0 mm	Extreme 61
19 Aug after	42.0 °C	15 %	37 km/h	0.0 mm	Extreme 65
20 Aug after	41.8 °C	19 %	31 km/h	0.1 mm	Very extreme 94

Before and after, from space

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

↔

Before · 2 Aug 2023

After · 17 Aug 2023

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 10 August 2023 the air beside the fire reached 11 µg/m³ of PM2.5, but no daily average passed the WHO guideline (15).

PM2.5 peak11 µg/m³

Days over the guideline0 days

PM1016 µg/m³

Optical depth0.21

789101112

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 · 14Every 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 Cedar Top Fire last?: The official perimeter only gives the start date (9 August 2023). The end comes from the heat detections inside the perimeter: it burned until 10 August 2023 (2 days from 9 August 2023), 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 935 hectares (9.4 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 2 counties: Knox (893 ha, 0.4 %); Baylor (41 ha, 0.0 %).
What was the weather like?: During the fire the temperature reached 43.0 °C, humidity dropped to 16 % and gusts hit 54 km/h. The fire danger index (FWI) reached 76, class Very extreme.
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

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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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How we know this

Perimeter: MTBS (US Geological Survey and US Forest Service), 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. 14 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