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TH · Thailand · –

Wiang Haeng fire, 11 March 2020 เวียงแหง · Wiang Haeng, Pai

Out · last detection 6 Apr 2020, 19:25 UTC

The fire started on 11 March 2020 in Wiang Haeng, Thailand, and satellites saw it burning for 26 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 3,614 hectares from heat detections, spread across 2 municipalities.

It is the 28th largest in Chiang Mai Province since 2016 (of 319 with a page). Number 61 in Thailand in 2020, of 457.

Burnt area
3,614ha
GWIS perimeter (Copernicus)
Duration
26days
11 Mar 2020 – 5 Apr 2020
Municipalities hit
2
districts
Started on
11 Mar
2020
Heat detections
149
in a single hotspot: 64 MW
Danger at start
39
Very high · FWI index
Average daily power
30MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 11 Mar5 Apr
6 Apr 2020

How it evolved, day by day

11 Mar 2020 · 3 MW · 1 12 Mar 2020 · 3 MW · 2 16 Mar 2020 · 9 MW · 4 17 Mar 2020 · 52 MW · 20 18 Mar 2020 · 20 MW · 13 19 Mar 2020 · 9 MW · 7 20 Mar 2020 · 3 MW · 3 21 Mar 2020 · 5 MW · 3 22 Mar 2020 · 21 MW · 10 23 Mar 2020 · 56 MW · 7 24 Mar 2020 · 26 MW · 11 25 Mar 2020 · 32 MW · 9 26 Mar 2020 · 25 MW · 5 27 Mar 2020 · 79 MW · 16 28 Mar 2020 · 165 MW · 10 29 Mar 2020 · 12 MW · 7 30 Mar 2020 · 3 MW · 2 31 Mar 2020 · 52 MW · 6 1 Apr 2020 · 87 MW · 10 2 Apr 2020 · 4 MW · 1 5 Apr 2020 · 1 MW · 1 6 Apr 2020 · 1 MW · 1
11 Mar 19 Mar 24 Mar 28 Mar 5 Apr

Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.

The weather it burned in

38°high
49km/h · peak gust
15%lowest humidity

It had gone more than two months without rain (1 mm or more) when it started. Rain came after the fire: 2.7 mm on 14 Apr.

This area had burned before

49% of the perimeter overlaps earlier fires recorded since 2016: 1,071 ha in 2016, 449 ha in 2017, 622 ha in 2018, 692 ha in 2019. Part of it burned more than once, so the yearly figures add up to more than the 1,760 ha that had burned before.

How big is it?

10 km
It burned the equivalent of 2.3% of the area of London (36 km² against 1,583 km²).

London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).

This compares size, not location: both shapes are at the same scale, north up, centred on each other.

What happened to each town

  1. Wiang Haeng เวียงแหง where it started
    3,536 ha reached on 11 Mar
    5.0 %
  2. Pai ปาย
    95 ha reached on 16 Mar
    0.0 %

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 2020
Built-up area0.99 ha
Residents≈ 150

Inside the perimeter there were about 0.99 hectares of built-up land and about 150 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)

Started with 60 days without rain: 14 % of the area in Thailand

Day High Min. humidity Peak gust Rain Danger (FWI)
11 Mar 35.5 °C 20 % 38 km/h 0.0 mm Very high 39
12 Mar 35.5 °C 21 % 35 km/h 0.0 mm Very high 38
13 Mar 36.4 °C 23 % 26 km/h 0.0 mm High 36
14 Mar 36.1 °C 25 % 19 km/h 0.0 mm High 37
15 Mar 36.7 °C 23 % 34 km/h 0.0 mm Very high 39
16 Mar 35.6 °C 21 % 43 km/h 0.0 mm Very high 43
17 Mar 35.5 °C 21 % 41 km/h 0.0 mm Very high 42
18 Mar 35.5 °C 21 % 44 km/h 0.0 mm Very high 44
19 Mar 35.2 °C 20 % 31 km/h 0.0 mm Very high 39
20 Mar 34.8 °C 23 % 47 km/h 0.0 mm Very high 44
21 Mar 33.2 °C 26 % 49 km/h 0.4 mm Very high 46
22 Mar 32.2 °C 26 % 47 km/h 0.6 mm High 35
23 Mar 33.1 °C 24 % 44 km/h 0.0 mm Very high 38
24 Mar 34.1 °C 21 % 49 km/h 0.0 mm Very high 42
25 Mar 33.6 °C 20 % 48 km/h 0.0 mm Very high 43
26 Mar 34.2 °C 20 % 47 km/h 0.0 mm Very high 43
27 Mar 35.2 °C 23 % 37 km/h 0.0 mm Very high 40
28 Mar 36.5 °C 23 % 32 km/h 0.0 mm High 38
29 Mar 36.4 °C 26 % 38 km/h 0.0 mm Very high 41
30 Mar 36.9 °C 25 % 38 km/h 0.0 mm Very high 41
31 Mar 37.7 °C 23 % 36 km/h 0.0 mm Very high 41
1 Apr 37.4 °C 17 % 41 km/h 0.0 mm Very high 46
2 Apr 36.6 °C 18 % 46 km/h 0.0 mm Very high 48
3 Apr 37.3 °C 15 % 42 km/h 0.0 mm Very high 47
4 Apr 36.9 °C 18 % 37 km/h 0.0 mm Very high 46
5 Apr 36.2 °C 21 % 46 km/h 0.0 mm Very high 50
6 Apr after 35.2 °C 27 % 49 km/h 0.0 mm Very high 46
7 Apr after 35.3 °C 21 % 45 km/h 0.0 mm Very high 44
8 Apr after 35.4 °C 23 % 30 km/h 0.0 mm Very high 40
9 Apr after 34.9 °C 26 % 31 km/h 0.0 mm Very high 39
10 Apr after 36.0 °C 18 % 45 km/h 0.0 mm Very high 45
11 Apr after 35.8 °C 27 % 31 km/h 0.1 mm Very high 40
12 Apr after 35.5 °C 29 % 32 km/h 0.0 mm Very high 39
13 Apr after 36.6 °C 17 % 40 km/h 0.1 mm Very high 47
14 Apr after 33.9 °C 33 % 32 km/h 2.7 mm Moderate 14

Its twins: fires that started in the same weather

It started with an FWI of 39.3, a minimum humidity of 20% and more than two months without rain. Fires in the area that started in weather like this since 2016: 29.

FWI at the start 39.3
Minimum humidity 20 %
Days without rain 60+
this fire chosen twins rest of the area
Almost identicalSimilar

Outlines of the closest twins

Pai fire, March 2019
1,388 ha 13 days FWI 38.7 Min. humidity 20 % 44 km away, in 2019

First rain (1 mm or more) after it ended: none in the following ten days.

What happened to them

12 days
median duration
2,107 ha
median area
100 %
went past 1,000 ha
2.4 mm
rain at the end (median; 9 of 29 had it)

It was 1.7 times larger than the median of its twins and lasted 26 days, against 12 days.

Only 6 of its 29 twins burned more. The weather on the first day does not explain everything: the wind in the following days, the fuel and the firefighting also count. In 20 of 29, not even 1 mm fell in the ten days after the end: they went out without rain. In the rest, the first rainy day brought a median of 2.4 mm.

This is a bank of analogues: it shows what usually happens, not what will happen. With fewer than 15 twins we give no figures. How we calculate it

How it ended

2.7 mmfirst rain
14 Apr9 days after it ended
49km/h · max. gust

It was considered over on 5 Apr, and on 14 Apr 2.7 mm fell. We do not know whether the rain or the firefighters put it out. Twins with rain when they ended: 9 of 29, with a median of 2.4 mm.

Weather on this page: Open-Meteo.com (CC BY 4.0) · Copernicus Climate Change Service (ERA5)

How a twin is chosen

  • Same area: fires that have already ended, less than 250 km from this one, since 2016.
  • Same start: we compare the FWI on the first day, the minimum humidity that day and the run of days without rain before it. The slider sets how much they may differ.
  • Only pages with final weather data (ERA5 reanalysis) calculated in the same way as this fire’s; agricultural and grass burns and pages with data under review are left out.
  • Fires burning at the same time as this one (a week before or after) are left out: they share the same spell of weather and do not count as a precedent.
  • They are sorted by similarity, and the outlines of the first five are drawn.

How we calculate it

Before and after, from space

Drag the line to compare the same ground before the fire and after it.

Before · 4 Mar 2020
After · 12 Apr 2020

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 · 149Every satellite heat detection, one by one, with time, satellite, power and coordinates.
⬇ Download CSV Times in UTC. Each detection is a 375 m pixel: a large fire yields hundreds per pass.
Date and timeSatelliteFRP (MW)LatLon

Other fires nearby

All fires in Thailand

Frequently asked questions

How long did the Wiang Haeng fire last?
According to the heat detections seen by satellite inside the perimeter, it burned from 11 March 2020 to 5 April 2020 (26 days). The perimeter dates it from 16 March 2020 to 29 March 2020.
How much area did it burn?
The perimeter GWIS (Copernicus) rebuilt from heat detections is 3,614 hectares (36.1 km²). It is an estimate: official national figures may differ.
Which municipalities burned?
The fire entered 2 municipalities: Wiang Haeng (3,536 ha, 5.0 %); Pai (95 ha, 0.0 %).
What was the weather like?
During the fire the temperature reached 37.7 °C, humidity dropped to 15 % and gusts hit 49 km/h. The fire danger index (FWI) reached 50, 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.
How did the fires that started in similar weather in this area end?
Fires less than 250 km away that started since 2016 with a similar FWI, humidity and dry spell: 29. Their median duration was 12 days and their median area 2,107 ha; 100 % went past 1,000 ha. Only 6 of its 29 twins burned more. The weather on the first day does not explain everything: the wind in the following days, the fuel and the firefighting also count. In 20 of 29, not even 1 mm fell in the ten days after the end: they went out without rain. In the rest, the first rainy day brought a median of 2.4 mm.

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 · 2 Changes in area, dates, name, official record or merged pages, compared every night since 24 October 2026.
  1. Last day with fire: 29 March 2020 → 5 April 2020.
  2. Start date: 16 March 2020 → 11 March 2020.

RSS Changes to this page With cross-checks and a citable version

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
What do you think is wrong?

We will only use your email to reply about this report. Privacy. This is not an emergency service: if there is a fire now, call 199 · 191.

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 16 March 2020 to 29 March 2020. 149 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.

How we build fire pages: methodology

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.