Burned area
satellite only3,025ha
Perimeter published by GWIS (Copernicus).
- Source
- GWIS (Copernicus)
- Date
- 19 Apr 2023 – 25 Apr 2023
+− cross-check
No official record is matched to this page to compare it with.
LA · Laos · –
Nhot Ou fire, 19 April 2023 Nhot Ou, Boon Neua
Out · last measured on 25 Apr 2023
The fire started on 19 April 2023 in Nhot Ou, Laos, and satellites saw it burning for 7 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 3,025 hectares from heat detections, spread across 2 municipalities.
It is the 18th largest in Phongsaly since 2016 (of 50 with a page). Number 113 in Laos in 2023, of 239.
Use this data
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Use this data
Fire page data · version 2026-10-24matches the official recordwith caveatssatellite onlymodel
When copying, the sentence is
Tick the figures you want: they make up the lede and the CSV.
Duration by satellite
satellite only7days
19 Apr 2023 to 25 Apr 2023: first and last day with fire on the page.
- Source
- GWIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- 19 Apr 2023 – 25 Apr 2023
+− cross-check
Satellites pass a few times a day and cloud or smoke can hide the fire: a lack of detections is not an official extinction. Each country’s emergency service declares a fire contained or out.
Start
satellite only19 Apr 2023
First day with fire seen by the satellites or the perimeter.
- Source
- GWIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- 19 Apr 2023
+− cross-check
No official record is matched to this page, so the alert time and the cause are not known here.
Danger at the start
model39.1FWI · very high
Fire Weather Index (Canadian system) computed by WorldFires for the day the fire started. Consecutive days without rain before: 20.
- Source
- WorldFires calculation (Canadian FWI system)
- Date
- 19 Apr 2023, local noon
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
This is an index computed from weather model data, not a measurement of the fire nor an official warning. Danger warnings are issued by each country’s authority. Emergency number and official warnings
Weather during the fire
model36.9°C · 20% RH
High of 36.9 °C and minimum humidity of 20% on 19 April 2023; gusts of 48 km/h on 21 April 2023.
- Source
- weather model at the fire’s grid cell
- Date
- 19 Apr 2023 – 25 Apr 2023
- Model
- ERA5 0,25° (ECMWF · Copernicus C3S) · Open-Meteo.com
+− cross-check
These are model values for a cell of about 25 km, not from a weather station: they may differ from what was measured on the ground.
Living inside
model≈ 200people
Estimated residents inside the perimeter and 0.00 ha of built-up area (100 m grid, epoch 2025).
- Source
- GHSL R2023A · JRC
- Date
- calculated on 24 October 2026
+− cross-check
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.
This page’s change log has been kept since 24 October 2026: every night what it publishes is compared and the difference is logged. Anything earlier is reconstructed from each source’s date and marked as reconstructed.
Show
-
· reconstructed weatherWeather and FWI computed from the ERA5 reanalysis
-
· reconstructed GHSLPopulation and built-up area computed
What was saved on 24 October 2026
Every night a snapshot of what the page shows is saved. If anything changes, it appears in the list as a log entry.
- Area
- 3,025 ha
- Dates
- 19 Apr 2023 – 25 Apr 2023
- Name
- Nhot Ou
- Official record
- —
Versioned permanent link
https://worldfires.org/en/fire/nhot-ou-2023-04-2?v=2026-10-24A version keeps the area, dates, name and official record; the area as it was logged (changes under 2% are not logged). The map, hotspots and weather always show today’s data.
Citation
A lede of about 60 words figures only, no adjectives
CSV for this fire nhot-ou-2023-04-2.csv · daily, no individual hotspots
| fecha | focos_viirs | frp_mw | tmax_c | tmin_c | hr_min_pct | viento_max_kmh | racha_max_kmh | precip_mm | fwi | clase_fwi | dentro_del_incendio |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2023-04-19 | 0 | 0 | 36.9 | 20.3 | 20 | 15.5 | 47.2 | 0 | 39.1 | muy_alto | 1 |
| 2023-04-20 | 0 | 0 | 36.2 | 19.2 | 24 | 17.2 | 46.8 | 0 | 41.4 | muy_alto | 1 |
| 2023-04-21 | 0 | 0 | 35.9 | 19 | 23 | 15.3 | 47.5 | 0 | 40.2 | muy_alto | 1 |
| 2023-04-22 | 0 | 0 | 35.2 | 19.7 | 27 | 14.7 | 45.4 | 0.1 | 39.5 | muy_alto | 1 |
| 2023-04-23 | 0 | 0 | 35.7 | 21 | 24 | 10.7 | 38.9 | 0.4 | 36.4 | alto | 1 |
| 2023-04-24 | 0 | 0 | 33.6 | 20.8 | 29 | 11.1 | 37.8 | 0 | 35.1 | alto | 1 |
| 2023-04-25 | 0 | 0 | 35.2 | 19.4 | 24 | 9.8 | 33.5 | 0 | 34.4 | alto | 1 |
| 2023-04-26 | 0 | 0 | 28.1 | 19.3 | 55 | 9.5 | 38.2 | 12.6 | 2 | muy_bajo | 0 |
It is generated in your browser from this page’s data: one file per fire, aggregated by day and without individual hotspots.
Live widget for your story
It updates itself while the fire is still active and links to this page. Free, with the attribution shown at the bottom.
Sources for this page: GWIS (Copernicus), NASA FIRMS (VIIRS), ERA5 (ECMWF/Copernicus C3S) · Open-Meteo.com (CC BY 4.0), GHSL (JRC). Open-Meteo.com · How we build fire pages: methodology
We have the GWIS perimeter for this fire, but the VIIRS sensors did not capture it in enough detail: no day-by-day evolution, but the split by municipality is there.
- Burnt area
- 3,025ha
- GWIS perimeter (Copernicus)
- Duration
- 7days
- 19 Apr 2023 – 25 Apr 2023
- Municipalities hit
- 2
- districts
- Started on
- 19 Apr
- 2023
- Danger at start
- 39
- Very high · FWI index
Where it burned
The weather it burned in
37°high
48km/h · peak gust
20%lowest humidity
It had gone 20 days without rain (1 mm or more) when it started. Rain came after the fire: 12.6 mm on 26 Apr.
This area had burned before
53% of the perimeter overlaps earlier fires recorded since 2016: 283 ha in 2016, 72 ha in 2017, 773 ha in 2019, 480 ha in 2020, 739 ha in 2022. Part of it burned more than once, so the yearly figures add up to more than the 1,617 ha that had burned before.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Paris boundary: geoBoundaries · Institut national de l'information géographique et forestière (IGN-F) (Etalab Open License 2.0).
Madrid boundary: geoBoundaries · Open Data ESRI, IGN Central Registry of Cartography Area (CC BY 4.0).
Berlin boundary: geoBoundaries · Federal Agency for Cartography and Geodesy (dl-de/by-2-0).
This compares size, not location: both shapes are at the same scale, north up, centred on each other.
What happened to each town
-
Nhot Ou where it started2,818 ha0.9 %
-
216 ha0.2 %
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 2025Built-up area< 0.1 ha
Residents≈ 200
Inside the perimeter there were about 0.00 hectares of built-up land and about 200 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) |
|---|---|---|---|---|---|
| 19 Apr | 36.9 °C | 20 % | 47 km/h | 0.0 mm | Very high 39 |
| 20 Apr | 36.2 °C | 24 % | 47 km/h | 0.0 mm | Very high 41 |
| 21 Apr | 35.9 °C | 23 % | 48 km/h | 0.0 mm | Very high 40 |
| 22 Apr | 35.2 °C | 27 % | 45 km/h | 0.1 mm | Very high 40 |
| 23 Apr | 35.7 °C | 24 % | 39 km/h | 0.4 mm | High 36 |
| 24 Apr | 33.6 °C | 29 % | 38 km/h | 0.0 mm | High 35 |
| 25 Apr | 35.2 °C | 24 % | 34 km/h | 0.0 mm | High 34 |
| 26 Apr after | 28.1 °C | 55 % | 38 km/h | 12.6 mm | Very low 2 |
Its twins: fires that started in the same weather
It started with an FWI of 39.1, a minimum humidity of 20% and 20 days without rain. Fires in the area that started in weather like this since 2016: 23.
FWI at the start
39.1
Minimum humidity
20 %
Days without rain
20
this fire
chosen twins
rest of the area
Almost identicalSimilar
Outlines of the closest twins
This fire · Nhot Ou fire, 19 April 2023
3,025 ha
7 days
FWI 39.1
Min. humidity 20 %
Long fire, April 2020
2,606 ha
9 days
FWI 41.9
Min. humidity 21 %
162 km away, in 2020
First rain (1 mm or more) after it ended: 21.2 mm on 13 Apr.
Tonpheung fire, April 2016
3,655 ha
13 days
FWI 41.8
Min. humidity 22 %
220 km away, in 2016
First rain (1 mm or more) after it ended: 8.6 mm on 1 May.
Long fire, March 2020
2,495 ha
10 days
FWI 40.6
Min. humidity 19 %
165 km away, in 2020
First rain (1 mm or more) after it ended: 21.2 mm on 13 Apr.
Sing fire, March 2020
4,910 ha
13 days
FWI 37.6
Min. humidity 17 %
83 km away, in 2020
First rain (1 mm or more) after it ended: 2.0 mm on 8 Apr.
Pakbeng fire, March 2020
2,001 ha
16 days
FWI 40.6
Min. humidity 21 %
214 km away, in 2020
First rain (1 mm or more) after it ended: 1.0 mm on 12 Apr.
What happened to them
- 11 days
- median duration
- 2,984 ha
- median area
- 100 %
- went past 1,000 ha
- 7.1 mm
- rain at the end (median; 22 of 23 had it)
It burned an area similar to its twins (3,025 ha against a median of 2,984 ha) and lasted 7 days, against 11 days.
In 1 of 23, 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 7.1 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
12.6 mmfirst rain
26 Aprthe day after it ended
48km/h · max. gust
It was considered over on 25 Apr, and on 26 Apr 12.6 mm fell. We do not know whether the rain or the firefighters put it out. Twins with rain when they ended: 22 of 23, with a median of 7.1 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.
Before and after, from space
Drag the line to compare the same ground before the fire and after it.
↔
Before · 12 Apr 2023
After · 2 May 2023
Sentinel-2 did not pass over on that day. Try another date, or use false colour, which is daily.
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 · CopernicusOn 17 April 2023 the air beside the fire reached 88 µg/m³ of PM2.5. That day averaged 46: 3.1 times the WHO daily guideline (15).
PM2.5 peak88 µg/m³
Days over the guideline12 days
PM10125 µg/m³
Optical depth1.07
WHO 15
17 Apr20 Apr23 Apr26 Apr
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)
Other fires nearby
- 2,857 haBoon Neua30 March 2020 · 6 days · 10 km away
- 2,237 haNhot Ou8 April 2023 · 7 days · 19 km away
- 2,908 haPhongsaly9 April 2026 · 7 days · 22 km away
- 2,205 haNhot OuMarch 2020 · 10 days · 27 km away
- 3,446 haPhongsaly5 April 2026 · 13 days · 29 km away
- 2,407 haBoon Neua10 April 2023 · 6 days · 30 km away
Frequently asked questions
- How long did the Nhot Ou fire last?
- GWIS (Copernicus) dates it between 19 April 2023 and 25 April 2023: 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 3,025 hectares (30.2 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire entered 2 municipalities: Nhot Ou (2,818 ha, 0.9 %); Boon Neua (216 ha, 0.2 %).
- What was the weather like?
- During the fire the temperature reached 36.9 °C, humidity dropped to 20 % and gusts hit 48 km/h. The fire danger index (FWI) reached 41, class Very 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.
- 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: 23. Their median duration was 11 days and their median area 2,984 ha; 100 % went past 1,000 ha. In 1 of 23, 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 7.1 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.
Satellite cross-check
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 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
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. No 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.
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.