How long did the Phrao fire last?

GWIS (Copernicus) dates it between 12 April 2026 and 18 April 2026: 7 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 1,820 hectares (18.2 km²). It is an estimate: official national figures may differ.

Which municipalities burned?

The fire only entered Phrao (1,828 ha, 1.4 %).

What was the weather like?

During the fire the temperature reached 37.9 °C, humidity dropped to 25 % and gusts hit 36 km/h. The fire danger index (FWI) reached 36, 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 · 2026-04-12 → 2026-04-18

Phrao fire, 12 April 2026 พร้าว · Phrao

Out · last detection 18 Apr 2026, 19:27 UTC

The fire started on 12 April 2026 in Phrao, Thailand, and satellites saw it burning for 7 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 1,820 hectares from heat detections, spread across a single municipality.

It is the 159th largest in Chiang Mai Province since 2016 (of 399 with a page). Number 335 in Thailand in 2026, of 689.

The power measured by the satellite is low (8.0 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…

Suggestions: Phrao · 2020 Phrao · 2016 Doi Saket · 2026 Wiang Pa Pao · 2020

Burnt area: 1,820ha; GWIS perimeter (Copernicus)
Duration: 7days; 12 Apr 2026 – 18 Apr 2026
Municipalities hit: 1; districts
Started on: 12 Apr; 2026
Heat detections: 23; in a single hotspot: 8 MW
Danger at start: 32; High · FWI index
Average daily power: 11MW; detected power per day, on average

HOTSPOTS BY DAY 12 Apr18 Apr

Play back 18 Apr 2026

How it evolved, day by day

12 Apr 13 Apr 14 Apr 15 Apr 16 Apr 17 Apr 18 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

36km/h · peak gust

25%lowest humidity

It had gone 29 days without rain (1 mm or more) when it started. Rain came after the fire: 3.6 mm on 25 Apr.

This area had burned before

50% of the perimeter overlaps earlier fires recorded since 2016: 601 ha in 2016, 221 ha in 2017, 424 ha in 2020, 13 ha in 2021, 424 ha in 2023. Part of it burned more than once, so the yearly figures add up to more than the 913 ha that had burned before.

How big is it?

It burned the equivalent of 1.1% of the area of London (18 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

Phrao พร้าว where it started

1,828 ha

1.4 %

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 2025

Built-up area4.8 ha

Residents≈ 450

Inside the perimeter there were about 4.8 hectares of built-up land and about 450 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)
12 Apr	36.9 °C	25 %	31 km/h	0.0 mm	High 32
13 Apr	37.2 °C	30 %	32 km/h	0.0 mm	High 34
14 Apr	37.1 °C	31 %	33 km/h	0.0 mm	High 34
15 Apr	37.9 °C	27 %	36 km/h	0.0 mm	High 36
16 Apr	36.8 °C	33 %	28 km/h	0.0 mm	High 34
17 Apr	36.5 °C	33 %	23 km/h	0.1 mm	High 33
18 Apr	36.3 °C	37 %	28 km/h	0.0 mm	High 32
19 Apr after	36.7 °C	33 %	36 km/h	0.1 mm	High 35
20 Apr after	35.9 °C	38 %	33 km/h	0.0 mm	High 32
21 Apr after	36.9 °C	39 %	31 km/h	0.0 mm	High 32
22 Apr after	37.9 °C	35 %	29 km/h	0.0 mm	High 31
23 Apr after	35.0 °C	44 %	28 km/h	0.1 mm	High 28
24 Apr after	36.7 °C	36 %	26 km/h	0.1 mm	High 28
25 Apr after	30.9 °C	63 %	31 km/h	3.6 mm	Very low 5

Before and after, from space

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

↔

Before · 5 Apr 2026

After · 25 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 169 µg/m³ of PM2.5. That day averaged 96: 6.4 times the WHO daily guideline (15).

PM2.5 peak169 µg/m³

Days over the guideline12 days

PM10192 µg/m³

Optical depth1.98

WHO 15

101112131415161718192021

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 · 23Every 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 Phrao fire last?: GWIS (Copernicus) dates it between 12 April 2026 and 18 April 2026: 7 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 1,820 hectares (18.2 km²). It is an estimate: official national figures may differ.
Which municipalities burned?: The fire only entered Phrao (1,828 ha, 1.4 %).
What was the weather like?: During the fire the temperature reached 37.9 °C, humidity dropped to 25 % and gusts hit 36 km/h. The fire danger index (FWI) reached 36, 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

NASA FIRMS ↗
GWIS · Copernicus ↗

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.

RSS Changes to this page

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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Dates or duration Place or towns Burned area Name It was not a wildfire Same fire as another page Something else

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.

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. 23 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.

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.

Where it burned