Burned area
satellite only914ha
Perimeter published by MTBS (USGS/USFS).
- Source
- MTBS (USGS/USFS)
- Date
- 29 Aug 2023 – 4 Sept 2023
+− cross-check
No official record is matched to this page to compare it with.
US · United States · –
Unwelcome Fire, August 2023 Jefferson
Out · last detection 4 Sept 2023, 08:11 UTC
The fire started on 29 August 2023 in Jefferson, United States, and satellites saw it burning for 7 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 914 hectares, spread across a single county.
It is the 194th largest in Texas since 2016 (of 327 with a page). Number 167 in United States in 2023, of 305.
The power measured by the satellite is low (21.4 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
Use this data
Fire page data · version 2026-10-24matches the official recordwith caveatssatellite onlymodel
When copying, the sentence is
Tick the figures you want: they make up the lede and the CSV.
Duration by satellite
satellite only7days
29 Aug 2023 to 4 Sept 2023: first and last day with fire on the page.
- Source
- MTBS (USGS/USFS) · NASA FIRMS · VIIRS
- Date
- last detection: 4 Sept 2023, 08:11 UTC
+− cross-check
Satellites pass a few times a day and cloud or smoke can hide the fire: a lack of detections is not an official extinction. Each country’s emergency service declares a fire contained or out.
Start
satellite only29 Aug 2023
First day with fire seen by the satellites or the perimeter.
- Source
- MTBS (USGS/USFS) · NASA FIRMS · VIIRS
- Date
- 29 Aug 2023
+− cross-check
No official record is matched to this page, so the alert time and the cause are not known here.
Hotspots
satellite only32
VIIRS detections at 375 m. Most intense hotspot: 21 MW.
- Source
- NASA FIRMS · VIIRS (Suomi NPP)
- Date
- 29 Aug 2023 – 4 Sept 2023
+− cross-check
There is no official record to compare with. Each hotspot is a pixel detected in one satellite pass, not a separate fire.
The worst day
satellite only343MW
Total radiative power on 29 August 2023; hotspots that day: 29.
- Source
- NASA FIRMS · VIIRS (FRP)
- Date
- 29 Aug 2023
+− cross-check
Fire radiative power (FRP) measures the energy the fire gives off when the satellite passes. Added up by day, it compares intensity, not area.
Danger at the start
model25.3FWI · high
Fire Weather Index (Canadian system) computed by WorldFires for the day the fire started. Consecutive days without rain before: 6.
- Source
- WorldFires calculation (Canadian FWI system)
- Date
- 29 Aug 2023, local noon
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
This is an index computed from weather model data, not a measurement of the fire nor an official warning. Danger warnings are issued by each country’s authority. Emergency number and official warnings
Weather during the fire
model33.9°C · 37% RH
High of 33.9 °C and minimum humidity of 37% on 30 August 2023; gusts of 36 km/h on 29 August 2023.
- Source
- weather model at the fire’s grid cell
- Date
- 29 Aug 2023 – 4 Sept 2023
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
These are model values for a cell of about 25 km, not from a weather station: they may differ from what was measured on the ground.
This page’s change log has been kept since 24 October 2026: every night what it publishes is compared and the difference is logged. Anything earlier is reconstructed from each source’s date and marked as reconstructed.
Show
-
· reconstructed weatherWeather and FWI computed from the ERA5 reanalysis
-
· reconstructed GHSLPopulation and built-up area computed
What was saved on 24 October 2026
Every night a snapshot of what the page shows is saved. If anything changes, it appears in the list as a log entry.
- Area
- 914 ha
- Dates
- 29 Aug 2023 – 4 Sept 2023
- Name
- Unwelcome
- Official record
- —
Versioned permanent link
https://worldfires.org/en/fire/unwelcome-fire-2023-08?v=2026-10-24A version keeps the area, dates, name and official record; the area as it was logged (changes under 2% are not logged). The map, hotspots and weather always show today’s data.
Citation
A lede of about 60 words figures only, no adjectives
CSV for this fire unwelcome-fire-2023-08.csv · daily, no individual hotspots
| fecha | focos_viirs | frp_mw | tmax_c | tmin_c | hr_min_pct | viento_max_kmh | racha_max_kmh | precip_mm | fwi | clase_fwi | dentro_del_incendio |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2023-08-29 | 29 | 343 | 33.2 | 27.5 | 47 | 21.7 | 36.4 | 0 | 25.3 | alto | 1 |
| 2023-08-30 | 0 | 0 | 33.9 | 26.8 | 37 | 23.2 | 32.4 | 0 | 31.7 | alto | 1 |
| 2023-08-31 | 0 | 0 | 31.7 | 26.3 | 46 | 15.8 | 24.5 | 0 | 26.2 | alto | 1 |
| 2023-09-01 | 0 | 0 | 32 | 26.9 | 51 | 16.9 | 27 | 0 | 25.2 | alto | 1 |
| 2023-09-02 | 0 | 0 | 30.6 | 27.9 | 72 | 17.6 | 26.3 | 1.9 | 7.4 | bajo | 1 |
| 2023-09-03 | 0 | 0 | 31.2 | 28.3 | 65 | 26.9 | 34.2 | 0.1 | 17.1 | moderado | 1 |
| 2023-09-04 | 3 | 8 | 29.7 | 26.1 | 76 | 24.7 | 31.3 | 9.3 | 1.1 | muy_bajo | 1 |
| 2023-09-05 | 0 | 0 | 30.7 | 28 | 75 | 21.3 | 29.9 | 2.8 | 2.4 | muy_bajo | 0 |
It is generated in your browser from this page’s data: one file per fire, aggregated by day and without individual hotspots.
Live widget for your story
It updates itself while the fire is still active and links to this page. Free, with the attribution shown at the bottom.
Sources for this page: MTBS (USGS/USFS), NASA FIRMS (VIIRS), ERA5 (ECMWF/Copernicus C3S) · Open-Meteo.com (CC BY 4.0), GHSL (JRC). Open-Meteo.com · How we build fire pages: methodology
- Burnt area
- 914ha
- official perimeter (MTBS / NIFC)
- Duration
- ≈ 7days
- 29 Aug 2023 – 4 Sept 2023
- Counties hit
- 1
- counties
- Started on
- 29 Aug
- 2023
- Heat detections
- 32
- in a single hotspot: 21 MW
- Danger at start
- 25
- High · FWI index
- Average daily power
- 176MW
- detected power per day, on average
Where it burned
HOTSPOTS BY DAY
29 Aug4 Sept
4 Sept 2023
How it evolved, day by day
29 Aug
4 Sept
Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.
The weather it burned in
34°high
36km/h · peak gust
37%lowest humidity
It had gone 6 days without rain (1 mm or more) when it started. Rain came after the fire: 2.8 mm on 5 Sept.
This area had burned before
94% of the perimeter overlaps earlier fires recorded since 2016: 853 ha in 2018, 1 ha in 2019, 765 ha in 2022. Part of it burned more than once, so the yearly figures add up to more than the 855 ha that had burned before.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Paris boundary: geoBoundaries · Institut national de l'information géographique et forestière (IGN-F) (Etalab Open License 2.0).
Madrid boundary: geoBoundaries · Open Data ESRI, IGN Central Registry of Cartography Area (CC BY 4.0).
Berlin boundary: geoBoundaries · Federal Agency for Cartography and Geodesy (dl-de/by-2-0).
This compares size, not location: both shapes are at the same scale, north up, centred on each other.
What happened to each county
-
Jefferson where it started905 ha reached on 29 Aug0.4 %
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 2025Built-up area0.20 ha
Residents< 20
Inside the perimeter there were about 0.20 hectares of 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) |
|---|---|---|---|---|---|
| 29 Aug | 33.2 °C | 47 % | 36 km/h | 0.0 mm | High 25 |
| 30 Aug | 33.9 °C | 37 % | 32 km/h | 0.0 mm | High 32 |
| 31 Aug | 31.7 °C | 46 % | 24 km/h | 0.0 mm | High 26 |
| 1 Sept | 32.0 °C | 51 % | 27 km/h | 0.0 mm | High 25 |
| 2 Sept | 30.6 °C | 72 % | 26 km/h | 1.9 mm | Low 7 |
| 3 Sept | 31.2 °C | 65 % | 34 km/h | 0.1 mm | Moderate 17 |
| 4 Sept | 29.7 °C | 76 % | 31 km/h | 9.3 mm | Very low 1 |
| 5 Sept after | 30.7 °C | 75 % | 30 km/h | 2.8 mm | Very low 2 |
Before and after, from space
Drag the line to compare the same ground before the fire and after it.
↔
Before · 22 Aug 2023
After · 11 Sept 2023
Sentinel-2 did not pass over on that day. Try another date, or use false colour, which is daily.
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 29 August 2023 the air beside the fire reached 21 µg/m³ of PM2.5. That day averaged 16: 1.1 times the WHO daily guideline (15).
PM2.5 peak21 µg/m³
Days over the guideline1 day
PM1030 µg/m³
Optical depth0.49
WHO 15
27 Aug29 Aug31 Aug
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 · 32Every 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
- 2,270 haNew Years Wf JeffersonJanuary 2018 · 4 days · 4 km away
- 3,834 haH And H Complex JeffersonOctober 2023 · 17 days · 21 km away
- 3,093 haWf Perkins Blowout JeffersonOctober 2017 · 2 days · 28 km away
- 1,989 haUnit 1 JeffersonSeptember 2022 · 2 days · 31 km away
- 1,917 haHoldover JeffersonJuly 2021 · 2 days · 36 km away
Frequently asked questions
- How long did the Unwelcome Fire last?
- The official perimeter only gives the start date (29 August 2023). The end comes from the heat detections inside the perimeter: it burned until 4 September 2023 (7 days from 29 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 914 hectares (9.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.
- Which counties burned?
- The fire only entered Jefferson (905 ha, 0.4 %).
- What was the weather like?
- During the fire the temperature reached 33.9 °C, humidity dropped to 37 % and gusts hit 36 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 · 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.
RSS Changes to this page With cross-checks and a citable version
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.
- 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. 32 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.