Pai fire, January 2021 Pang Mapha, Mueang Mae Hong Son, Pai
The fire started on 20 January 2021 in Pai, Thailand, and satellites saw it burning for 6 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 1,472 hectares from heat detections, spread across 3 municipalities.
It is the 386th largest in Mae Hong Son Province since 2016 (of 668 with a page). Number 124 in Thailand in 2021, of 268.
The power measured by the satellite is low (4.8 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.
- Burnt area
- 1,472ha
- GWIS perimeter (Copernicus)
- Duration
- 6days
- 20 Jan 2021 – 25 Jan 2021
- Municipalities hit
- 3
- districts
- Started on
- 20 Jan
- 2021
- Heat detections
- 44
- in a single hotspot: 5 MW
- Danger at start
- 24
- High · FWI index
- Energy released
- 86MW
- sum of detected power
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 more than two months without rain (1 mm or more) when it started.
This area had burned before
99% of the perimeter overlaps earlier fires recorded since 2016: 1,105 ha in 2016, 580 ha in 2017, 110 ha in 2018, 1,266 ha in 2019, 849 ha in 2020. Part of it burned more than once, so the yearly figures add up to more than the 1,454 ha that had burned before.
- 728 ha Mueang Mae Hong Son fire, February 2020 3,419 ha in total; the hectares shown are those it shares with this fire
- 186 ha Pang Mapha fire, February 2016 1,083 ha in total; the hectares shown are those it shares with this fire
- 178 ha Mueang Mae Hong Son fire, February 2019 4,260 ha in total; the hectares shown are those it shares with this fire
- 83 ha Mueang Mae Hong Son fire, February 2020 1,443 ha in total; the hectares shown are those it shares with this fire
- 64 ha Pai fire, March 2016 1,114 ha in total; the hectares shown are those it shares with this fire
What happened to each town
-
1,123 ha reached on 20 Jan1.0 %
-
200 ha reached on 24 Jan0.1 %
-
Pai where it started154 ha reached on 24 Jan0.1 %
Burnt area inside each municipality, from crossing the GWIS perimeter with administrative boundaries. The distance is from the town centre 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) |
|---|---|---|---|---|---|
| 18 Jan | 28.1 °C | 44 % | 43 km/h | 0.0 mm | High 24 |
| 19 Jan | 28.8 °C | 42 % | 25 km/h | 0.0 mm | Moderate 20 |
| 20 Jan | 29.2 °C | 39 % | 33 km/h | 0.0 mm | High 22 |
| 21 Jan | 30.0 °C | 36 % | 27 km/h | 0.0 mm | High 21 |
| 22 Jan | 30.1 °C | 38 % | 25 km/h | 0.0 mm | High 22 |
| 23 Jan | 30.1 °C | 39 % | 32 km/h | 0.0 mm | High 23 |
| 24 Jan | 30.7 °C | 31 % | 30 km/h | 0.0 mm | High 24 |
| 25 Jan | 31.9 °C | 32 % | 26 km/h | 0.0 mm | High 24 |
| 26 Jan after | 32.9 °C | 31 % | 26 km/h | 0.0 mm | High 25 |
| 27 Jan after | 33.0 °C | 35 % | 28 km/h | 0.0 mm | High 26 |
| 28 Jan after | 33.3 °C | 34 % | 22 km/h | 0.0 mm | High 25 |
| 29 Jan after | 32.2 °C | 45 % | 34 km/h | 0.0 mm | High 25 |
| 30 Jan after | 30.2 °C | 52 % | 34 km/h | 0.8 mm | Moderate 16 |
| 31 Jan after | 31.1 °C | 38 % | 32 km/h | 0.2 mm | High 22 |
| 1 Feb after | 31.9 °C | 32 % | 32 km/h | 0.0 mm | High 26 |
| 2 Feb after | 32.0 °C | 27 % | 30 km/h | 0.0 mm | High 28 |
| 3 Feb after | 32.9 °C | 21 % | 27 km/h | 0.0 mm | High 31 |
| 4 Feb after | 33.2 °C | 22 % | 24 km/h | 0.0 mm | High 31 |
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 · 44Every 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 Pai fire last?
- GWIS (Copernicus) dates it between 20 January 2021 and 25 January 2021: 6 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 1,472 hectares (14.7 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire entered 3 municipalities: Pang Mapha (1,123 ha, 1.0 %); Mueang Mae Hong Son (200 ha, 0.1 %); Pai (154 ha, 0.1 %).
- What was the weather like?
- During the fire the temperature reached 31.9 °C, humidity dropped to 31 % and gusts hit 43 km/h. The fire danger index (FWI) reached 24, 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
Satellite cross-check
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
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.