Pai fire, April 2023 Pai
The fire started on 3 April 2023 in Pai, Thailand, and satellites saw it burning for 4 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 4,149 hectares from heat detections, spread across a single municipality.
It is the 87th largest in Mae Hong Son Province since 2016 (of 668 with a page). Number 42 in Thailand in 2023, of 500.
The power measured by the satellite is low (9.6 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
- 4,149ha
- GWIS perimeter (Copernicus)
- Duration
- 4days
- 3 Apr 2023 – 6 Apr 2023
- Municipalities hit
- 1
- districts
- Started on
- 3 Apr
- 2023
- Heat detections
- 128
- in a single hotspot: 10 MW
- Danger at start
- 37
- High · FWI index
- Energy released
- 320MW
- 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 14 days without rain (1 mm or more) when it started.
This area had burned before
93% of the perimeter overlaps earlier fires recorded since 2016: 322 ha in 2016, 1,786 ha in 2017, 726 ha in 2018, 1,237 ha in 2019, 2,669 ha in 2020, 1,472 ha in 2021, 48 ha in 2022. Part of it burned more than once, so the yearly figures add up to more than the 3,854 ha that had burned before.
- 988 ha Pai fire, February 2020 1,655 ha in total; the hectares shown are those it shares with this fire
- 845 ha Pai fire, March 2020 1,724 ha in total; the hectares shown are those it shares with this fire
- 351 ha Pai fire, February 2021 1,172 ha in total; the hectares shown are those it shares with this fire
- 107 ha Pai fire, February 2020 1,764 ha in total; the hectares shown are those it shares with this fire
What happened to each town
-
Pai where it started4,166 ha reached on 28 Mar1.8 %
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) |
|---|---|---|---|---|---|
| 28 Mar | 38.4 °C | 18 % | 40 km/h | 0.0 mm | High 37 |
| 29 Mar | 36.6 °C | 24 % | 47 km/h | 0.0 mm | Very high 40 |
| 30 Mar | 37.2 °C | 27 % | 38 km/h | 0.0 mm | High 38 |
| 31 Mar | 37.3 °C | 27 % | 38 km/h | 0.0 mm | High 37 |
| 1 Apr | 37.4 °C | 29 % | 42 km/h | 0.0 mm | High 36 |
| 2 Apr | 36.5 °C | 29 % | 50 km/h | 0.1 mm | Very high 40 |
| 3 Apr | 35.7 °C | 32 % | 49 km/h | 0.0 mm | High 38 |
| 4 Apr | 36.9 °C | 23 % | 44 km/h | 0.0 mm | High 37 |
| 5 Apr | 38.3 °C | 22 % | 29 km/h | 0.0 mm | High 35 |
| 6 Apr | 38.1 °C | 28 % | 24 km/h | 0.0 mm | High 34 |
| 7 Apr after | 38.6 °C | 31 % | 31 km/h | 0.0 mm | High 35 |
| 8 Apr after | 38.6 °C | 32 % | 28 km/h | 0.4 mm | High 34 |
| 9 Apr after | 38.9 °C | 27 % | 35 km/h | 0.0 mm | Very high 39 |
| 10 Apr after | 39.9 °C | 26 % | 32 km/h | 0.0 mm | High 37 |
| 11 Apr after | 39.2 °C | 28 % | 35 km/h | 0.0 mm | Very high 38 |
| 12 Apr after | 39.5 °C | 28 % | 33 km/h | 0.0 mm | High 38 |
| 13 Apr after | 39.5 °C | 31 % | 35 km/h | 0.0 mm | Very high 39 |
| 14 Apr after | 40.7 °C | 25 % | 31 km/h | 0.0 mm | High 38 |
| 15 Apr after | 40.5 °C | 27 % | 24 km/h | 0.0 mm | High 37 |
| 16 Apr after | 39.1 °C | 31 % | 32 km/h | 0.0 mm | Very high 38 |
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 5 April 2023 the air beside the fire reached 60 µg/m³ of PM2.5. That day averaged 39: 2.6 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 · 128Every 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 3 April 2023 and 6 April 2023: 4 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 4,149 hectares (41.5 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire only entered Pai (4,166 ha, 1.8 %).
- What was the weather like?
- During the fire the temperature reached 38.4 °C, humidity dropped to 18 % and gusts hit 50 km/h. The fire danger index (FWI) reached 40, class Very 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.