Dan Sai fire, 18 March 2021 ด่านซ้าย · Dan Sai
The fire started on 18 March 2021 in Dan Sai, Thailand, and satellites saw it burning for 5 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 2,011 hectares from heat detections, spread across a single municipality.
It is the 44th largest in Loei Province since 2016 (of 113 with a page). Number 51 in Thailand in 2021, of 187.
The power measured by the satellite is low (22.0 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
- 2,011ha
- GWIS perimeter (Copernicus)
- Duration
- 5days
- 18 Mar 2021 – 22 Mar 2021
- Municipalities hit
- 1
- districts
- Started on
- 18 Mar
- 2021
- Heat detections
- 59
- in a single hotspot: 22 MW
- Danger at start
- 17
- Moderate · FWI index
- Average daily power
- 53MW
- 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 6 days without rain (1 mm or more) when it started.
This area had burned before
99% of the perimeter overlaps earlier fires recorded since 2016: 1,620 ha in 2016, 1,235 ha in 2017, 1,488 ha in 2018, 1,765 ha in 2019, 1,422 ha in 2020. Part of it burned more than once, so the yearly figures add up to more than the 1,981 ha that had burned before.
- 1,757 ha Dan Sai fire, March 2019 4,640 ha in total; the hectares shown are those it shares with this fire
- 1,364 ha Dan Sai fire, March 2016 6,404 ha in total; the hectares shown are those it shares with this fire
- 1,339 ha Dan Sai fire, March 2018 2,046 ha in total; the hectares shown are those it shares with this fire
- 1,049 ha Dan Sai fire, February 2020 1,577 ha in total; the hectares shown are those it shares with this fire
- 261 ha Dan Sai fire, March 2017 1,684 ha in total; the hectares shown are those it shares with this fire
- 170 ha Dan Sai fire, April 2017 2,593 ha in total; the hectares shown are those it shares with this fire
- 33 ha Dan Sai fire, March 2018 1,102 ha in total; the hectares shown are those it shares with this fire
- 20 ha Dan Sai fire, February 2020 1,537 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
-
2,022 ha1.5 %
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 were about 0.90 hectares of built-up land and about 80 residents (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) |
|---|---|---|---|---|---|
| 11 Mar | 32.4 °C | 49 % | 17 km/h | 0.0 mm | Moderate 17 |
| 12 Mar | 32.0 °C | 51 % | 20 km/h | 0.0 mm | Moderate 16 |
| 13 Mar | 31.4 °C | 53 % | 17 km/h | 0.5 mm | Moderate 16 |
| 14 Mar | 31.4 °C | 54 % | 21 km/h | 0.8 mm | Moderate 12 |
| 15 Mar | 31.9 °C | 54 % | 30 km/h | 0.2 mm | Moderate 14 |
| 16 Mar | 32.7 °C | 52 % | 24 km/h | 0.0 mm | Moderate 15 |
| 17 Mar | 33.5 °C | 49 % | 26 km/h | 0.2 mm | Moderate 17 |
| 18 Mar | 34.1 °C | 50 % | 20 km/h | 0.0 mm | Moderate 16 |
| 19 Mar | 34.0 °C | 51 % | 27 km/h | 0.4 mm | Moderate 17 |
| 20 Mar | 34.9 °C | 46 % | 27 km/h | 0.3 mm | Moderate 19 |
| 21 Mar | 35.8 °C | 43 % | 22 km/h | 1.0 mm | Moderate 16 |
| 22 Mar | 31.2 °C | 45 % | 38 km/h | 0.0 mm | High 22 |
| 23 Mar after | 31.8 °C | 46 % | 24 km/h | 0.0 mm | Moderate 18 |
| 24 Mar after | 33.2 °C | 43 % | 22 km/h | 0.0 mm | Moderate 19 |
| 25 Mar after | 34.4 °C | 42 % | 16 km/h | 0.0 mm | Moderate 20 |
| 26 Mar after | 35.0 °C | 43 % | 30 km/h | 0.7 mm | Moderate 20 |
| 27 Mar after | 35.6 °C | 44 % | 27 km/h | 0.3 mm | High 21 |
| 28 Mar after | 35.0 °C | 46 % | 33 km/h | 0.0 mm | High 23 |
| 29 Mar after | 34.8 °C | 44 % | 40 km/h | 0.3 mm | High 25 |
| 30 Mar after | 33.3 °C | 41 % | 40 km/h | 0.0 mm | High 25 |
| 31 Mar after | 35.1 °C | 38 % | 29 km/h | 0.0 mm | High 26 |
| 1 Apr after | 35.6 °C | 38 % | 24 km/h | 0.0 mm | High 25 |
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 · 59Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 6,404 haDan Sai ด่านซ้ายMarch 2016 · 10 days · 1 km away
- 4,640 haDan Sai ด่านซ้าย10 March 2019 · 7 days · 2 km away
- 7,219 haLom Kao หล่มเก่า8 April 2026 · 14 days · 26 km away
- 7,064 haLom Kao หล่มเก่าFebruary 2021 · 9 days · 31 km away
- 6,306 haPhu Ruea ภูเรือ3 April 2026 · 13 days · 32 km away
- 5,317 haNa Haeo นาแห้ว21 March 2023 · 14 days · 34 km away
Frequently asked questions
- How long did the Dan Sai fire last?
- GWIS (Copernicus) dates it between 18 March 2021 and 22 March 2021: 5 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 2,011 hectares (20.1 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire only entered Dan Sai (2,022 ha, 1.5 %).
- What was the weather like?
- During the fire the temperature reached 35.8 °C, humidity dropped to 43 % and gusts hit 38 km/h. The fire danger index (FWI) reached 22, 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 from the perimeter: the VIIRS detections inside it did not change them. 59 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.