Mae Lao fire, March 2023 แม่ลาว · Mae Suai, Phan, Mueang Chiang Rai
The fire started on 21 March 2023 in Mae Lao, Thailand, and satellites saw it burning for 34 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 23,457 hectares from heat detections, spread across 4 municipalities.
It is the largest fire in Chiang Rai Province since 2016 (of 187 with a page). The largest in Thailand in 2023, of 369.
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- Burnt area
- 23,457ha
- GWIS perimeter (Copernicus)
- Duration
- 34days
- 21 Mar 2023 – 23 Apr 2023
- Municipalities hit
- 4
- districts
- Started on
- 21 Mar
- 2023
- Heat detections
- 1,210
- in a single hotspot: 44 MW
- Danger at start
- 20
- Moderate · FWI index
- Average daily power
- 150MW
- 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: 3.7 mm on 26 Apr.
This area had burned before
70% of the perimeter overlaps earlier fires recorded since 2016: 7,719 ha in 2016, 13,063 ha in 2019, 5,303 ha in 2020, 2,306 ha in 2021. Part of it burned more than once, so the yearly figures add up to more than the 16,429 ha that had burned before.
- 2,480 ha Phan fire, April 2019 3,127 ha in total; the hectares shown are those it shares with this fire
- 1,945 ha Phan fire, March 2019 2,100 ha in total; the hectares shown are those it shares with this fire
- 1,416 ha Mae Suai fire, April 2019 3,790 ha in total; the hectares shown are those it shares with this fire
- 1,277 ha Mueang Chiang Rai fire, April 2016 3,590 ha in total; the hectares shown are those it shares with this fire
- 1,229 ha Phan fire, March 2021 1,622 ha in total; the hectares shown are those it shares with this fire
- 960 ha Mae Suai fire, April 2016 21,629 ha in total; the hectares shown are those it shares with this fire
- 908 ha Mae Suai fire, March 2016 1,597 ha in total; the hectares shown are those it shares with this fire
- 756 ha Mueang Chiang Rai fire, March 2020 1,786 ha in total; the hectares shown are those it shares with this fire
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
-
Mae Suai แม่สรวย11,907 ha reached on 22 Mar8.4 %
-
Phan พาน8,342 ha reached on 21 Mar8.5 %
-
Mueang Chiang Rai เมืองเชียงราย2,686 ha reached on 23 Mar1.7 %
-
639 ha reached on 21 Mar2.9 %
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 9.1 hectares of built-up land and about 950 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) |
|---|---|---|---|---|---|
| 21 Mar | 34.8 °C | 35 % | 28 km/h | 0.3 mm | Moderate 20 |
| 22 Mar | 36.6 °C | 27 % | 35 km/h | 0.0 mm | High 30 |
| 23 Mar | 37.1 °C | 26 % | 32 km/h | 1.1 mm | High 26 |
| 24 Mar | 36.2 °C | 29 % | 23 km/h | 0.0 mm | High 26 |
| 25 Mar | 35.6 °C | 30 % | 20 km/h | 0.0 mm | High 26 |
| 26 Mar | 36.8 °C | 28 % | 22 km/h | 0.0 mm | High 28 |
| 27 Mar | 36.1 °C | 33 % | 23 km/h | 0.0 mm | High 29 |
| 28 Mar | 37.7 °C | 21 % | 36 km/h | 0.0 mm | Very high 39 |
| 29 Mar | 36.3 °C | 27 % | 28 km/h | 0.0 mm | High 33 |
| 30 Mar | 36.6 °C | 30 % | 20 km/h | 0.0 mm | High 31 |
| 31 Mar | 35.8 °C | 34 % | 22 km/h | 0.0 mm | High 30 |
| 1 Apr | 36.7 °C | 34 % | 30 km/h | 0.0 mm | High 33 |
| 2 Apr | 37.4 °C | 27 % | 36 km/h | 0.0 mm | High 36 |
| 3 Apr | 35.5 °C | 30 % | 33 km/h | 0.0 mm | High 36 |
| 4 Apr | 36.8 °C | 27 % | 21 km/h | 0.0 mm | High 32 |
| 5 Apr | 36.3 °C | 27 % | 19 km/h | 0.0 mm | High 32 |
| 6 Apr | 36.4 °C | 32 % | 19 km/h | 0.0 mm | High 33 |
| 7 Apr | 37.1 °C | 34 % | 20 km/h | 0.0 mm | High 33 |
| 8 Apr | 36.8 °C | 39 % | 24 km/h | 0.0 mm | High 32 |
| 9 Apr | 38.3 °C | 33 % | 33 km/h | 0.0 mm | High 34 |
| 10 Apr | 38.5 °C | 32 % | 24 km/h | 0.0 mm | High 32 |
| 11 Apr | 38.5 °C | 33 % | 20 km/h | 0.0 mm | High 32 |
| 12 Apr | 38.5 °C | 29 % | 20 km/h | 0.0 mm | High 32 |
| 13 Apr | 39.1 °C | 34 % | 21 km/h | 0.0 mm | High 33 |
| 14 Apr | 39.7 °C | 30 % | 20 km/h | 0.0 mm | High 33 |
| 15 Apr | 38.5 °C | 30 % | 21 km/h | 0.0 mm | High 34 |
| 16 Apr | 39.7 °C | 31 % | 28 km/h | 0.0 mm | High 36 |
| 17 Apr | 38.7 °C | 34 % | 27 km/h | 0.0 mm | High 36 |
| 18 Apr | 39.6 °C | 34 % | 21 km/h | 0.0 mm | High 33 |
| 19 Apr | 39.5 °C | 31 % | 23 km/h | 0.0 mm | High 34 |
| 20 Apr | 39.0 °C | 33 % | 23 km/h | 0.1 mm | High 36 |
| 21 Apr | 38.5 °C | 35 % | 24 km/h | 0.0 mm | High 36 |
| 22 Apr | 37.5 °C | 37 % | 26 km/h | 2.9 mm | Moderate 17 |
| 23 Apr | 39.2 °C | 32 % | 28 km/h | 0.1 mm | High 32 |
| 24 Apr after | 36.4 °C | 38 % | 25 km/h | 0.1 mm | High 30 |
| 25 Apr after | 38.4 °C | 30 % | 16 km/h | 0.0 mm | High 31 |
| 26 Apr after | 34.0 °C | 49 % | 38 km/h | 3.7 mm | Low 10 |
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 March 2023 the air beside the fire reached 178 µg/m³ of PM2.5. That day averaged 98: 6.5 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 · 1,210Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 12,910 haPhan พานMarch 2026 · 29 days · 27 km away
- 14,912 haMae Suai แม่สรวย25 March 2026 · 30 days · 32 km away
- 21,629 haMae Suai แม่สรวย1 April 2016 · 27 days · 33 km away
- 12,779 haWiang Pa Pao เวียงป่าเป้า23 March 2026 · 33 days · 35 km away
- 12,929 haWiang Pa Pao เวียงป่าเป้า20 March 2026 · 32 days · 36 km away
Frequently asked questions
- How long did the Mae Lao fire last?
- According to the heat detections seen by satellite inside the perimeter, it burned from 21 March 2023 to 23 April 2023 (34 days). The perimeter dates it from 21 March 2023 to 20 April 2023.
- How much area did it burn?
- The perimeter GWIS (Copernicus) rebuilt from heat detections is 23,457 hectares (234.6 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire entered 4 municipalities: Mae Suai (11,907 ha, 8.4 %); Phan (8,342 ha, 8.5 %); Mueang Chiang Rai (2,686 ha, 1.7 %); Mae Lao (639 ha, 2.9 %).
- What was the weather like?
- During the fire the temperature reached 39.7 °C, humidity dropped to 21 % and gusts hit 36 km/h. The fire danger index (FWI) reached 39, 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 · Emergency number and official warnings ›
Satellite cross-check
History of this page · 1 Changes in area, dates, name, official record or merged pages, compared every night since 24 October 2026.
- Last day with fire: 20 April 2023 → 23 April 2023.
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; 6 polygons grouped in this page.
- Dates adjusted with the VIIRS detections inside the perimeter, which said 21 March 2023 to 20 April 2023. 1,210 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 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.