How long did the Pai fire last?

GWIS (Copernicus) dates it between 8 April 2026 and 15 April 2026: 8 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 1,021 hectares (10.2 km²). It is an estimate: official national figures may differ.

Which municipalities burned?

The fire only entered Pai (1,026 ha, 0.4 %).

What was the weather like?

During the fire the temperature reached 37.4 °C, humidity dropped to 26 % and gusts hit 49 km/h. The fire danger index (FWI) reached 34, 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.

TH · Thailand · 2026-04-08 → 2026-04-15

Pai fire, 8 April 2026 Pai

Out · last detection 14 Apr 2026, 19:02 UTC

The fire started on 8 April 2026 in Pai, Thailand, and satellites saw it burning for 8 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 1,021 hectares from heat detections, spread across a single municipality.

It is the 645th largest in Mae Hong Son Province since 2016 (of 668 with a page). Number 857 in Thailand in 2026, of 880.

The power measured by the satellite is low (5.1 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: 1,021ha; GWIS perimeter (Copernicus)
Duration: 8days; 8 Apr 2026 – 15 Apr 2026
Municipalities hit: 1; districts
Started on: 8 Apr; 2026
Heat detections: 26; in a single hotspot: 5 MW
Danger at start: 27; High · FWI index
Energy released: 27MW; sum of detected power

Play back 14 Apr 2026

HOTSPOTS BY DAY 8 Apr15 Apr

How it evolved, day by day

891214

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

The weather it burned in

37°high

49km/h · peak gust

26%lowest humidity

It had gone 11 days without rain (1 mm or more) when it started. Rain came after the fire: 5.7 mm on 25 Apr.

This area had burned before

91% of the perimeter overlaps earlier fires recorded since 2016: 506 ha in 2016, 156 ha in 2017, 153 ha in 2019, 168 ha in 2020, 190 ha in 2021, 138 ha in 2023, 701 ha in 2024, 136 ha in 2025. Part of it burned more than once, so the yearly figures add up to more than the 931 ha that had burned before.

What happened to each town

Pai where it started

1,026 ha reached on 8 Apr

0.4 %

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)
2 Apr	36.5 °C	29 %	36 km/h	0.0 mm	High 27
3 Apr	37.1 °C	27 %	36 km/h	0.0 mm	High 28
4 Apr	35.7 °C	34 %	33 km/h	0.0 mm	High 27
5 Apr	35.9 °C	36 %	36 km/h	0.0 mm	High 28
6 Apr	35.5 °C	37 %	29 km/h	0.1 mm	High 26
7 Apr	35.3 °C	38 %	39 km/h	0.3 mm	High 28
8 Apr	36.2 °C	28 %	38 km/h	0.0 mm	High 30
9 Apr	35.0 °C	32 %	44 km/h	0.2 mm	High 32
10 Apr	35.3 °C	29 %	49 km/h	0.0 mm	High 33
11 Apr	35.5 °C	28 %	48 km/h	0.0 mm	High 34
12 Apr	36.5 °C	26 %	36 km/h	0.0 mm	High 32
13 Apr	37.0 °C	28 %	36 km/h	0.0 mm	High 32
14 Apr	36.9 °C	30 %	30 km/h	0.0 mm	High 30
15 Apr	37.4 °C	28 %	37 km/h	0.0 mm	High 34
16 Apr after	35.9 °C	31 %	30 km/h	0.0 mm	High 32
17 Apr after	36.0 °C	32 %	22 km/h	0.0 mm	High 31
18 Apr after	35.5 °C	36 %	30 km/h	0.0 mm	High 31
19 Apr after	36.3 °C	32 %	42 km/h	0.4 mm	High 35
20 Apr after	35.5 °C	35 %	35 km/h	0.0 mm	High 33
21 Apr after	36.9 °C	34 %	35 km/h	0.3 mm	High 34
22 Apr after	37.9 °C	30 %	35 km/h	0.2 mm	High 33
23 Apr after	35.8 °C	39 %	28 km/h	0.1 mm	High 30
24 Apr after	37.2 °C	32 %	24 km/h	0.0 mm	High 29
25 Apr after	32.6 °C	51 %	36 km/h	5.7 mm	Very low 5

Before and after, from space

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

↔

Before · 1 Apr 2026

After · 22 Apr 2026

Before After

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 · Copernicus

On 17 April 2026 the air beside the fire reached 128 µg/m³ of PM2.5. That day averaged 68: 4.6 times the WHO daily guideline (15).

PM2.5 peak128 µg/m³

Days over the guideline19 days

PM10143 µg/m³

Optical depth1.51

WHO 15

31123456789101112131415161718

Good Fair Moderate Poor Very poor Extremely poor

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 · 26Every 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 time	Satellite	FRP (MW)	Lat	Lon

Other fires nearby

All fires in Thailand ›

Frequently asked questions

How long did the Pai fire last?: GWIS (Copernicus) dates it between 8 April 2026 and 15 April 2026: 8 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 1,021 hectares (10.2 km²). It is an estimate: official national figures may differ.
Which municipalities burned?: The fire only entered Pai (1,026 ha, 0.4 %).
What was the weather like?: During the fire the temperature reached 37.4 °C, humidity dropped to 26 % and gusts hit 49 km/h. The fire danger index (FWI) reached 34, 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

NASA FIRMS ↗
GWIS · Copernicus ↗

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.

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What really happened?

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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.

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.

Where it burned