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Li fire, March 2023 ลี้ · Li, Sam Ngao

Out · last detection 8 Apr 2023, 07:28 UTC

The fire started on 31 March 2023 in Li, Thailand, and satellites saw it burning for 12 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 1,074 hectares from heat detections, spread across 2 municipalities.

It is the 350th largest in Chiang Mai Province since 2016 (of 399 with a page). Number 326 in Thailand in 2023, of 369.

The power measured by the satellite is low (14.8 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: Li · 2026Li · 2026Omkoi · 2026Sam Ngao · 2025

Burnt area
1,074ha
GWIS perimeter (Copernicus)
Duration
12days
31 Mar 2023 – 11 Apr 2023
Municipalities hit
2
districts
Started on
31 Mar
2023
Heat detections
28
in a single hotspot: 15 MW
Danger at start
28
High · FWI index
Average daily power
21MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 31 Mar11 Apr
8 Apr 2023

How it evolved, day by day

31 Mar 2023 · 1 MW · 1 1 Apr 2023 · 2 MW · 1 3 Apr 2023 · 13 MW · 4 4 Apr 2023 · 42 MW · 10 5 Apr 2023 · 65 MW · 11 8 Apr 2023 · 4 MW · 1
31 Mar 1 Apr 3 Apr 4 Apr 5 Apr 8 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

36°high
41km/h · peak gust
25%lowest humidity

It had gone 9 days without rain (1 mm or more) when it started.

This area had burned before

80% of the perimeter overlaps earlier fires recorded since 2016: 310 ha in 2016, 296 ha in 2017, 66 ha in 2019, 216 ha in 2020, 525 ha in 2021. Part of it burned more than once, so the yearly figures add up to more than the 854 ha that had burned before.

How big is it?

10 km
It burned the equivalent of 0.7% of the area of London (11 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. Li ลี้ where it started
    1,065 ha reached on 31 Mar
    0.6 %
  2. Sam Ngao สามเงา
    16 ha
    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.

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)
31 Mar 34.8 °C 33 % 28 km/h 0.1 mm High 28
1 Apr 35.4 °C 32 % 24 km/h 0.0 mm High 28
2 Apr 35.6 °C 28 % 41 km/h 0.0 mm High 33
3 Apr 34.5 °C 30 % 41 km/h 0.0 mm High 34
4 Apr 35.5 °C 29 % 35 km/h 0.0 mm High 33
5 Apr 36.1 °C 25 % 28 km/h 0.0 mm High 29
6 Apr 36.3 °C 29 % 20 km/h 0.0 mm High 30
7 Apr 36.5 °C 32 % 22 km/h 0.0 mm High 32
8 Apr 36.2 °C 33 % 22 km/h 0.0 mm High 32
9 Apr 36.6 °C 30 % 27 km/h 0.0 mm High 32
10 Apr 37.2 °C 30 % 28 km/h 0.0 mm High 32
11 Apr 37.9 °C 29 % 30 km/h 0.0 mm High 33
12 Apr after 37.0 °C 31 % 28 km/h 0.0 mm High 34
13 Apr after 38.0 °C 31 % 30 km/h 0.0 mm High 35
14 Apr after 39.0 °C 24 % 27 km/h 0.0 mm High 35
15 Apr after 38.6 °C 28 % 28 km/h 0.0 mm High 35

Before and after, from space

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

Before · 24 Mar 2023
After · 18 Apr 2023

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 31 March 2023 the air beside the fire reached 52 µg/m³ of PM2.5. That day averaged 36: 2.4 times the WHO daily guideline (15).

PM2.5 peak52 µg/m³
Days over the guideline9 days
PM1075 µg/m³
Optical depth1.45
303112345678
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 · 28Every 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 Li fire last?
According to the heat detections seen by satellite inside the perimeter, it burned from 31 March 2023 to 11 April 2023 (12 days). The perimeter dates it from 1 April 2023 to 5 April 2023.
How much area did it burn?
The perimeter GWIS (Copernicus) rebuilt from heat detections is 1,074 hectares (10.7 km²). It is an estimate: official national figures may differ.
Which municipalities burned?
The fire entered 2 municipalities: Li (1,065 ha, 0.6 %); Sam Ngao (16 ha, 0.0 %).
What was the weather like?
During the fire the temperature reached 36.1 °C, humidity dropped to 25 % and gusts hit 41 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 · 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: 5 April 2023 → 11 April 2023.
  2. Start date: 1 April 2023 → 31 March 2023.

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.

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 1 April 2023 to 5 April 2023. 28 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.

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.