Ust-Aldansky Ulus fire, August 2025 Ust-Aldansky Ulus
The fire started on 26 August 2025 in Ust-Aldansky Ulus, Russia, and satellites saw it burning for 7 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 5,759 hectares from heat detections, spread across a single municipality.
It is the 828th largest in Sakha Republic since 2016 (of 1422 with a page). Number 123 in Russia in 2025, of 246.
Compare with…
- Burnt area
- 5,759ha
- GWIS perimeter (Copernicus)
- Duration
- 7days
- 26 Aug 2025 – 1 Sept 2025
- Municipalities hit
- 1
- districts
- Started on
- 26 Aug
- 2025
- Heat detections
- 543
- in a single hotspot: 95 MW
- Danger at start
- 18
- Moderate · FWI index
- Average daily power
- 713MW
- detected power per day, on average
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 12 days without rain (1 mm or more) when it started.
This area had burned before
91% of the perimeter overlaps earlier fires recorded since 2016: 5,477 ha in 2017.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Moscow boundary: geoBoundaries · OpenStreetMap, Wambacher · © OpenStreetMap contributors (ODbL 1.0).
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).
This compares size, not location: both shapes are at the same scale, north up, centred on each other.
What happened to each town
-
Ust-Aldansky Ulus where it started5,845 ha0.3 %
Burnt area inside each municipality, from crossing the GWIS 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.
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) |
|---|---|---|---|---|---|
| 25 Aug | 25.7 °C | 30 % | 17 km/h | 0.1 mm | Moderate 18 |
| 26 Aug | 26.1 °C | 27 % | 18 km/h | 0.0 mm | Moderate 18 |
| 27 Aug | 25.8 °C | 32 % | 20 km/h | 0.0 mm | Moderate 21 |
| 28 Aug | 25.5 °C | 31 % | 35 km/h | 0.0 mm | High 23 |
| 29 Aug | 24.6 °C | 25 % | 30 km/h | 0.0 mm | High 22 |
| 30 Aug | 22.9 °C | 40 % | 21 km/h | 0.0 mm | Moderate 19 |
| 31 Aug | 24.1 °C | 35 % | 14 km/h | 0.1 mm | Moderate 17 |
| 1 Sept | 22.8 °C | 41 % | 20 km/h | 0.3 mm | Moderate 17 |
| 2 Sept after | 20.3 °C | 52 % | 23 km/h | 0.0 mm | Moderate 15 |
| 3 Sept after | 14.8 °C | 53 % | 37 km/h | 0.1 mm | Moderate 15 |
| 4 Sept after | 19.7 °C | 26 % | 32 km/h | 0.0 mm | Moderate 21 |
| 5 Sept after | 19.5 °C | 32 % | 22 km/h | 0.0 mm | Moderate 19 |
| 6 Sept after | 20.2 °C | 32 % | 20 km/h | 0.0 mm | Moderate 19 |
| 7 Sept after | 19.6 °C | 33 % | 19 km/h | 0.0 mm | Moderate 19 |
| 8 Sept after | 13.5 °C | 50 % | 31 km/h | 0.0 mm | Moderate 16 |
| 9 Sept after | 12.5 °C | 38 % | 24 km/h | 0.0 mm | Moderate 15 |
| 10 Sept after | 13.7 °C | 33 % | 18 km/h | 0.0 mm | Moderate 16 |
| 11 Sept after | 13.4 °C | 41 % | 29 km/h | 0.5 mm | Moderate 18 |
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.
The smoke
CAMS · CopernicusOn 30 August 2025 the air beside the fire reached 106 µg/m³ of PM2.5. That day averaged 59: 3.9 times the WHO daily guideline (15).
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 · 543Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 3,072 haUst-Aldansky UlusJune 2020 · 4 days · 13 km away
- 84,832 haUst-Aldansky Ulus5 July 2020 · 50 days · 16 km away
- 147,024 haKobyaysky UlusJune 2017 · 26 days · 17 km away
- 14,414 haNamsky Ulus28 July 2017 · 13 days · 23 km away
- 3,778 haKobyaysky Ulus3 August 2017 · 6 days · 26 km away
- 56,084 haKobyaysky Ulus8 July 2020 · 33 days · 34 km away
Frequently asked questions
- How long did the Ust-Aldansky Ulus fire last?
- GWIS (Copernicus) dates it between 26 August 2025 and 1 September 2025: 7 days between the first and last heat detection of the perimeter.
- How much area did it burn?
- The perimeter GWIS (Copernicus) rebuilt from heat detections is 5,759 hectares (57.6 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire only entered Ust-Aldansky Ulus (5,845 ha, 0.3 %).
- What was the weather like?
- During the fire the temperature reached 26.1 °C, humidity dropped to 25 % and gusts hit 35 km/h. The fire danger index (FWI) reached 23, class High.
- Where does this data come from?
- From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Russia (geoBoundaries). 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: 112 · Emergency number and official warnings ›
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.
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: GWIS (Copernicus), rebuilt from heat detections rather than mapped on imagery.
- Dates from the perimeter: the VIIRS detections inside it did not change them. 543 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.
Where this data comes from
The perimeter comes from the Copernicus Global Wildfire Information System (GWIS), which rebuilds it from MODIS and VIIRS heat detections and publishes it under CC BY 4.0. It is not measured on imagery as in Europe, so it is an estimate. Heat detections come from the VIIRS sensors aboard Suomi-NPP and NOAA-20, distributed by NASA FIRMS at 375 m resolution. Municipal boundaries come from geoBoundaries ADM2 (Open Data Commons Open Database License 1.0). The area per municipality is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ from each country’s official figure.