Pai fire, 26 February 2021 ปาย · Pai
The fire started on 26 February 2021 in Pai, Thailand, and satellites saw it burning for 10 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 1,026 hectares from heat detections, spread across a single municipality.
It is the 372th largest in Mae Hong Son Province since 2016 (of 387 with a page). Number 177 in Thailand in 2021, of 187.
The power measured by the satellite is low (13.6 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
Compare with…
- Burnt area
- 1,026ha
- GWIS perimeter (Copernicus)
- Duration
- 10days
- 26 Feb 2021 – 7 Mar 2021
- Municipalities hit
- 1
- districts
- Started on
- 26 Feb
- 2021
- Heat detections
- 37
- in a single hotspot: 14 MW
- Danger at start
- 25
- High · FWI index
- Average daily power
- 24MW
- 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 7 days without rain (1 mm or more) when it started.
This area had burned before
72% of the perimeter overlaps earlier fires recorded since 2016: 1 ha in 2016, 275 ha in 2017, 551 ha in 2019, 321 ha in 2020. Part of it burned more than once, so the yearly figures add up to more than the 735 ha that had burned before.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Bangkok 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
-
1,030 ha reached on 26 Feb0.4 %
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 2020Inside the perimeter there was no noticeable built-up land and almost nobody lived there (GHSL 2020, 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.
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) |
|---|---|---|---|---|---|
| 26 Feb | 31.0 °C | 24 % | 40 km/h | 0.0 mm | High 25 |
| 27 Feb | 29.4 °C | 30 % | 36 km/h | 0.0 mm | High 24 |
| 28 Feb | 30.8 °C | 29 % | 35 km/h | 0.0 mm | High 25 |
| 1 Mar | 32.0 °C | 25 % | 32 km/h | 0.0 mm | High 24 |
| 2 Mar | 32.2 °C | 21 % | 38 km/h | 0.0 mm | High 28 |
| 3 Mar | 31.9 °C | 28 % | 48 km/h | 0.0 mm | High 31 |
| 4 Mar | 32.3 °C | 25 % | 48 km/h | 0.0 mm | High 32 |
| 5 Mar | 32.1 °C | 18 % | 45 km/h | 0.0 mm | High 33 |
| 6 Mar | 31.6 °C | 16 % | 38 km/h | 0.0 mm | High 33 |
| 7 Mar | 32.4 °C | 18 % | 36 km/h | 0.0 mm | High 33 |
| 8 Mar after | 32.3 °C | 20 % | 37 km/h | 0.0 mm | High 34 |
| 9 Mar after | 32.9 °C | 20 % | 28 km/h | 0.0 mm | High 32 |
| 10 Mar after | 32.6 °C | 25 % | 35 km/h | 0.0 mm | High 33 |
| 11 Mar after | 32.9 °C | 27 % | 27 km/h | 0.0 mm | High 31 |
| 12 Mar after | 33.5 °C | 25 % | 30 km/h | 0.0 mm | High 32 |
| 13 Mar after | 34.2 °C | 20 % | 21 km/h | 0.0 mm | High 30 |
| 14 Mar after | 32.3 °C | 32 % | 35 km/h | 0.0 mm | High 31 |
| 15 Mar after | 34.0 °C | 25 % | 37 km/h | 0.0 mm | High 32 |
| 16 Mar after | 34.6 °C | 22 % | 35 km/h | 0.0 mm | High 33 |
| 17 Mar after | 35.2 °C | 23 % | 35 km/h | 0.0 mm | High 34 |
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.
Detections table · 37Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 16,424 haPang Mapha ปางมะผ้าFebruary 2024 · 24 days · 19 km away
- 30,775 haPai ปาย23 March 2026 · 28 days · 25 km away
- 32,440 haMueang Mae Hong Son เมืองแม่ฮ่องสอน4 March 2025 · 38 days · 29 km away
- 15,767 haMueang Mae Hong Son เมืองแม่ฮ่องสอน28 February 2024 · 22 days · 31 km away
- 133,850 haMueang Mae Hong Son เมืองแม่ฮ่องสอน19 March 2026 · 37 days · 33 km away
- 22,763 haPai ปาย24 March 2026 · 32 days · 38 km away
Frequently asked questions
- How long did the Pai fire last?
- According to the heat detections seen by satellite inside the perimeter, it burned from 26 February 2021 to 7 March 2021 (10 days). The perimeter dates it from 4 March 2021 to 7 March 2021.
- How much area did it burn?
- The perimeter GWIS (Copernicus) rebuilt from heat detections is 1,026 hectares (10.3 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire only entered Pai (1,030 ha, 0.4 %).
- What was the weather like?
- During the fire the temperature reached 32.4 °C, humidity dropped to 16 % and gusts hit 48 km/h. The fire danger index (FWI) reached 33, class High.
- Where does this data come from?
- From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Thailand (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: 199 · 191 · 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 adjusted with the VIIRS detections inside the perimeter, which said 4 March 2021 to 7 March 2021. 37 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 2020, 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 3.0 Intergovernmental Organisations (CC BY 3.0 IGO)). 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.