Ootsuki fire, January 2026 大月市 · Ootsuki, Uenohara
The fire started on 8 January 2026 in Ootsuki, Japan, and satellites saw it burning for 10 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 849 hectares from heat detections, spread across 2 municipalities.
Number 9 in Japan in 2026, of 59.
The power measured by the satellite is low (4.2 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
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- Burnt area
- 849ha
- GWIS perimeter (Copernicus)
- Duration
- 10days
- 8 Jan 2026 – 17 Jan 2026
- Municipalities hit
- 2
- municipalities
- Started on
- 8 Jan
- 2026
- Heat detections
- 14
- in a single hotspot: 4 MW
- Danger at start
- 0
- Very low · FWI index
- Average daily power
- 6MW
- 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 0 days without rain (1 mm or more) when it started. Rain came after the fire: 1.5 mm on 20 Jan.
This area had burned before
No earlier perimeters overlap this fire since 2016, when the satellite record begins.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Tokyo (without the islands) 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
-
565 ha2.0 %
-
Uenohara 上野原市285 ha1.7 %
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.
People and buildings inside the perimeter
GHSL 2025Inside the perimeter there were about 4.2 hectares of built-up land and about 150 residents (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) |
|---|---|---|---|---|---|
| 8 Jan | 6.3 °C | 28 % | 41 km/h | 0.0 mm | Very low 0 |
| 9 Jan | 5.1 °C | 29 % | 26 km/h | 0.0 mm | Very low 1 |
| 10 Jan | 8.3 °C | 21 % | 59 km/h | 0.0 mm | Very low 2 |
| 11 Jan | 6.5 °C | 29 % | 71 km/h | 0.0 mm | Very low 4 |
| 12 Jan | 4.3 °C | 25 % | 36 km/h | 0.0 mm | Very low 2 |
| 13 Jan | 7.7 °C | 47 % | 66 km/h | 0.2 mm | Very low 3 |
| 14 Jan | 6.2 °C | 28 % | 34 km/h | 0.0 mm | Very low 2 |
| 15 Jan | 8.0 °C | 33 % | 52 km/h | 0.0 mm | Very low 3 |
| 16 Jan | 12.7 °C | 21 % | 52 km/h | 0.0 mm | Very low 4 |
| 17 Jan | 12.9 °C | 10 % | 36 km/h | 0.0 mm | Low 6 |
| 18 Jan after | 9.0 °C | 45 % | 23 km/h | 0.0 mm | Very low 4 |
| 19 Jan after | 10.7 °C | 35 % | 35 km/h | 0.0 mm | Very low 4 |
| 20 Jan after | 6.7 °C | 51 % | 37 km/h | 1.5 mm | Very low 0 |
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 7 January 2026 the air beside the fire reached 58 µg/m³ of PM2.5. That day averaged 34: 2.2 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 · 14Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
Frequently asked questions
- How long did the Ootsuki fire last?
- GWIS (Copernicus) dates it between 8 January 2026 and 17 January 2026: 10 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 849 hectares (8.5 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire entered 2 municipalities: Ootsuki (565 ha, 2.0 %); Uenohara (285 ha, 1.7 %).
- What was the weather like?
- During the fire the temperature reached 12.9 °C, humidity dropped to 10 % and gusts hit 71 km/h. The fire danger index (FWI) reached 6, class Low.
- Where does this data come from?
- From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Japan (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: 119 · 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. 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.
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 (Creative Commons Attribution-ShareAlike 2.0). 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.