How long did the Hongsa fire last?

According to the heat detections seen by satellite inside the perimeter, it burned from 17 March 2023 to 4 April 2023 (19 days). The perimeter dates it from 18 March 2023 to 28 March 2023.

How much area did it burn?

The perimeter GWIS (Copernicus) rebuilt from heat detections is 2,500 hectares (25.0 km²). It is an estimate: official national figures may differ.

Which municipalities burned?

The fire only entered Hongsa (2,513 ha, 1.7 %).

What was the weather like?

During the fire the temperature reached 36.7 °C, humidity dropped to 26 % and gusts hit 47 km/h. The fire danger index (FWI) reached 30, class High.

Where does this data come from?

From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Laos (geoBoundaries). It is not an official report.

LA · Laos · 2023-03-17 → 2023-04-04

Hongsa fire, 17 March 2023 Hongsa

Out · last detection 4 Apr 2023, 19:33 UTC

The fire started on 17 March 2023 in Hongsa, Laos, and satellites saw it burning for 19 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 2,500 hectares from heat detections, spread across a single municipality.

It is the 99th largest in Xaignabouli since 2016 (of 161 with a page). Number 159 in Laos in 2023, of 239.

Compare with…

Suggestions: Hongsa · 2017 Nga · 2026 Hoon · 2020

Burnt area: 2,500ha; GWIS perimeter (Copernicus)
Duration: 19days; 17 Mar 2023 – 4 Apr 2023
Municipalities hit: 1; districts
Started on: 17 Mar; 2023
Heat detections: 81; in a single hotspot: 103 MW
Danger at start: 3; Very low · FWI index
Average daily power: 63MW; detected power per day, on average

HOTSPOTS BY DAY 17 Mar4 Apr

Play back 4 Apr 2023

How it evolved, day by day

17 Mar 21 Mar 23 Mar 25 Mar 27 Mar 4 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

37°high

47km/h · peak gust

26%lowest humidity

It had gone 0 days without rain (1 mm or more) when it started.

This area had burned before

41% of the perimeter overlaps earlier fires recorded since 2016: 275 ha in 2017, 230 ha in 2020, 940 ha in 2022. Part of it burned more than once, so the yearly figures add up to more than the 1,032 ha that had burned before.

275 ha Hongsa fire, April 2017 8,764 ha in total; the hectares shown are those it shares with this fire

How big is it?

It burned the equivalent of 1.6% of the area of London (25 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

Hongsa where it started

2,513 ha

1.7 %

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 area< 0.1 ha

Residents< 20

Inside the perimeter there was no noticeable built-up land and almost nobody lived there (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)
17 Mar	32.0 °C	45 %	32 km/h	3.6 mm	Very low 3
18 Mar	32.2 °C	48 %	35 km/h	2.8 mm	Very low 3
19 Mar	31.9 °C	54 %	38 km/h	5.0 mm	Very low 2
20 Mar	34.7 °C	38 %	36 km/h	0.2 mm	Low 10
21 Mar	34.4 °C	38 %	40 km/h	0.4 mm	Moderate 15
22 Mar	35.5 °C	30 %	43 km/h	0.0 mm	Moderate 21
23 Mar	36.7 °C	26 %	44 km/h	0.2 mm	High 24
24 Mar	35.6 °C	30 %	33 km/h	0.0 mm	High 23
25 Mar	35.8 °C	31 %	37 km/h	0.0 mm	High 24
26 Mar	34.8 °C	31 %	38 km/h	0.0 mm	High 26
27 Mar	34.1 °C	36 %	38 km/h	0.0 mm	High 23
28 Mar	33.4 °C	45 %	47 km/h	0.3 mm	High 21
29 Mar	33.9 °C	42 %	46 km/h	0.1 mm	Moderate 21
30 Mar	31.2 °C	56 %	34 km/h	1.6 mm	Low 7
31 Mar	34.1 °C	39 %	41 km/h	0.0 mm	Moderate 16
1 Apr	35.4 °C	35 %	41 km/h	0.2 mm	High 22
2 Apr	36.7 °C	26 %	44 km/h	0.0 mm	High 30
3 Apr	35.6 °C	29 %	41 km/h	0.0 mm	High 30
4 Apr	36.3 °C	27 %	38 km/h	0.0 mm	High 30
5 Apr after	36.1 °C	27 %	30 km/h	0.0 mm	High 29
6 Apr after	36.4 °C	28 %	25 km/h	0.0 mm	High 28
7 Apr after	35.3 °C	34 %	38 km/h	0.0 mm	High 30
8 Apr after	33.3 °C	48 %	40 km/h	0.0 mm	High 24
9 Apr after	34.7 °C	48 %	44 km/h	0.3 mm	High 26
10 Apr after	37.0 °C	35 %	37 km/h	0.0 mm	High 27
11 Apr after	38.5 °C	30 %	29 km/h	0.0 mm	High 29
12 Apr after	37.8 °C	32 %	29 km/h	0.0 mm	High 30
13 Apr after	37.3 °C	36 %	36 km/h	0.0 mm	High 31
14 Apr after	38.9 °C	32 %	31 km/h	0.0 mm	High 31

Before and after, from space

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

↔

Before · 10 Mar 2023

After · 11 Apr 2023

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 6 April 2023 the air beside the fire reached 337 µg/m³ of PM2.5. That day averaged 159: 11 times the WHO daily guideline (15).

PM2.5 peak337 µg/m³

Days over the guideline24 days

PM10482 µg/m³

Optical depth3.12

WHO 15

15161718192021222324252627282930311234567

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 · 81Every 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 Laos ›

Frequently asked questions

How long did the Hongsa fire last?: According to the heat detections seen by satellite inside the perimeter, it burned from 17 March 2023 to 4 April 2023 (19 days). The perimeter dates it from 18 March 2023 to 28 March 2023.
How much area did it burn?: The perimeter GWIS (Copernicus) rebuilt from heat detections is 2,500 hectares (25.0 km²). It is an estimate: official national figures may differ.
Which municipalities burned?: The fire only entered Hongsa (2,513 ha, 1.7 %).
What was the weather like?: During the fire the temperature reached 36.7 °C, humidity dropped to 26 % and gusts hit 47 km/h. The fire danger index (FWI) reached 30, class High.
Where does this data come from?: From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Laos (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.

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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What do you think is wrong?

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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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 18 March 2023 to 28 March 2023. 81 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