Burned area
satellite only10,432ha
Perimeter published by GWIS (Copernicus).
- Source
- GWIS (Copernicus)
- Date
- 31 Jul 2023 – 13 Aug 2023
+− cross-check
No official record is matched to this page to compare it with.
RU · Russia · –
Ust-Maysky Ulus fire, 31 July 2023 Ust-Maysky Ulus
Out · last detection 13 Aug 2023, 18:23 UTC
The fire started on 31 July 2023 in Ust-Maysky Ulus, Russia, and satellites saw it burning for 14 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 10,432 hectares from heat detections, spread across a single municipality.
It is the 450th largest in Sakha Republic since 2016 (of 1347 with a page). Number 100 in Russia in 2023, of 450.
Use this data
Compare with…
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 only14days
31 Jul 2023 to 13 Aug 2023: first and last day with fire on the page.
- Source
- GWIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- last detection: 13 Aug 2023, 18:23 UTC
+− 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 only31 Jul 2023
First day with fire seen by the satellites or the perimeter.
- Source
- GWIS (Copernicus) · NASA FIRMS · VIIRS
- Date
- 31 Jul 2023
+− cross-check
No official record is matched to this page, so the alert time and the cause are not known here.
Hotspots
satellite only1,753
VIIRS detections at 375 m. Most intense hotspot: 162 MW.
- Source
- NASA FIRMS · VIIRS (Suomi NPP)
- Date
- 31 Jul 2023 – 13 Aug 2023
+− cross-check
There is no official record to compare with. Each hotspot is a pixel detected in one satellite pass, not a separate fire.
The worst day
satellite only7,359MW
Total radiative power on 13 August 2023; hotspots that day: 381.
- Source
- NASA FIRMS · VIIRS (FRP)
- Date
- 13 Aug 2023
+− cross-check
Fire radiative power (FRP) measures the energy the fire gives off when the satellite passes. Added up by day, it compares intensity, not area.
Danger at the start
model24.8FWI · high
Fire Weather Index (Canadian system) computed by WorldFires for the day the fire started. Consecutive days without rain before: 9.
- Source
- WorldFires calculation (Canadian FWI system)
- Date
- 31 Jul 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
model29.7°C · 20% RH
High of 29.7 °C and minimum humidity of 20% on 13 August 2023; gusts of 44 km/h on 8 August 2023.
- Source
- weather model at the fire’s grid cell
- Date
- 31 Jul 2023 – 13 Aug 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.
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 GHSLPopulation and built-up area computed
-
· reconstructed weatherWeather and FWI computed from the ERA5 reanalysis
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
- 10,432 ha
- Dates
- 31 Jul 2023 – 13 Aug 2023
- Name
- Ust-Maysky Ulus
- Official record
- —
Versioned permanent link
https://worldfires.org/en/fire/ust-maysky-ulus-2023-07-13?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 ust-maysky-ulus-2023-07-13.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 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2023-07-31 | 4 | 4 | 25.4 | 9.5 | 35 | 13 | 28.8 | 0 | 24.8 | alto | 1 |
| 2023-08-01 | 3 | 48 | 17.6 | 10.7 | 47 | 14 | 33.5 | 0.7 | 16 | moderado | 1 |
| 2023-08-02 | 1 | 4 | 19.4 | 9.5 | 50 | 10.3 | 31.3 | 2.7 | 4.3 | muy_bajo | 1 |
| 2023-08-03 | 0 | 0 | 21.8 | 7.8 | 43 | 11.6 | 29.2 | 0.5 | 9.5 | bajo | 1 |
| 2023-08-04 | 15 | 24 | 25.7 | 8.4 | 29 | 11.2 | 26.6 | 0 | 19.6 | moderado | 1 |
| 2023-08-05 | 72 | 406 | 28.6 | 9 | 21 | 8.7 | 25.6 | 0 | 25.7 | alto | 1 |
| 2023-08-06 | 176 | 1,520 | 28 | 8.8 | 26 | 12.8 | 30.2 | 0 | 29.2 | alto | 1 |
| 2023-08-07 | 94 | 547 | 24 | 10.4 | 25 | 15.4 | 40 | 0 | 31.7 | alto | 1 |
| 2023-08-08 | 124 | 648 | 19.1 | 8.4 | 39 | 16.7 | 43.9 | 0 | 26.9 | alto | 1 |
| 2023-08-09 | 169 | 1,211 | 23.2 | 7.1 | 25 | 9.8 | 29.2 | 0 | 24.5 | alto | 1 |
| 2023-08-10 | 173 | 1,220 | 24 | 6.3 | 27 | 12.6 | 33.5 | 0.6 | 25.1 | alto | 1 |
| 2023-08-11 | 175 | 645 | 22.7 | 12.1 | 43 | 13.8 | 36.7 | 1.9 | 9.1 | bajo | 1 |
| 2023-08-12 | 366 | 2,411 | 27.7 | 12.3 | 24 | 12.6 | 29.5 | 0 | 24.3 | alto | 1 |
| 2023-08-13 | 381 | 7,359 | 29.7 | 10 | 20 | 16.1 | 40.3 | 0 | 35.1 | alto | 1 |
| 2023-08-14 | 0 | 0 | 22 | 14.5 | 39 | 16.3 | 40.7 | 4 | 5.9 | 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
- Burnt area
- 10,432ha
- GWIS perimeter (Copernicus)
- Duration
- 14days
- 31 Jul 2023 – 13 Aug 2023
- Municipalities hit
- 1
- districts
- Started on
- 31 Jul
- 2023
- Heat detections
- 1,753
- in a single hotspot: 162 MW
- Danger at start
- 25
- High · FWI index
- Average daily power
- 1.2GW
- detected power per day, on average
Where it burned
HOTSPOTS BY DAY
31 Jul13 Aug
13 Aug 2023
How it evolved, day by day
31 Jul
4 Aug
7 Aug
10 Aug
13 Aug
Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.
The weather it burned in
30°high
44km/h · peak gust
20%lowest humidity
It had gone 9 days without rain (1 mm or more) when it started. Rain came after the fire: 4.0 mm on 14 Aug.
This area had burned before
16% of the perimeter overlaps earlier fires recorded since 2016: 1,692 ha in 2021.
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Moscow boundary: geoBoundaries · OpenStreetMap, Wambacher · © OpenStreetMap contributors (ODbL 1.0).
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).
This compares size, not location: both shapes are at the same scale, north up, centred on each other.
What happened to each town
-
Ust-Maysky Ulus where it started10,422 ha reached on 31 Jul0.1 %
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< 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) |
|---|---|---|---|---|---|
| 31 Jul | 25.4 °C | 35 % | 29 km/h | 0.0 mm | High 25 |
| 1 Aug | 17.6 °C | 47 % | 34 km/h | 0.7 mm | Moderate 16 |
| 2 Aug | 19.4 °C | 50 % | 31 km/h | 2.7 mm | Very low 4 |
| 3 Aug | 21.8 °C | 43 % | 29 km/h | 0.5 mm | Low 10 |
| 4 Aug | 25.7 °C | 29 % | 27 km/h | 0.0 mm | Moderate 20 |
| 5 Aug | 28.6 °C | 21 % | 26 km/h | 0.0 mm | High 26 |
| 6 Aug | 28.0 °C | 26 % | 30 km/h | 0.0 mm | High 29 |
| 7 Aug | 24.0 °C | 25 % | 40 km/h | 0.0 mm | High 32 |
| 8 Aug | 19.1 °C | 39 % | 44 km/h | 0.0 mm | High 27 |
| 9 Aug | 23.2 °C | 25 % | 29 km/h | 0.0 mm | High 24 |
| 10 Aug | 24.0 °C | 27 % | 34 km/h | 0.6 mm | High 25 |
| 11 Aug | 22.7 °C | 43 % | 37 km/h | 1.9 mm | Low 9 |
| 12 Aug | 27.7 °C | 24 % | 30 km/h | 0.0 mm | High 24 |
| 13 Aug | 29.7 °C | 20 % | 40 km/h | 0.0 mm | High 35 |
| 14 Aug after | 22.0 °C | 39 % | 41 km/h | 4.0 mm | Low 6 |
Its twins: fires that started in the same weather
It started with an FWI of 24.8, a minimum humidity of 35% and 9 days without rain. Fires in the area that started in weather like this since 2017: 17.
FWI at the start
24.8
Minimum humidity
35 %
Days without rain
9
this fire
chosen twins
rest of the area
Almost identicalSimilar
Outlines of the closest twins
This fire · Ust-Maysky Ulus fire, 31 July 2023
10,432 ha
14 days
FWI 24.8
Min. humidity 35 %
Ust-Maysky Ulus fire, June 2021
43,982 ha
23 days
FWI 21.3
Min. humidity 35 %
11 km away, in 2021
First rain (1 mm or more) after it ended: 16.8 mm on 16 Jul.
Ust-Maysky Ulus fire, June 2024
14,256 ha
24 days
FWI 25.5
Min. humidity 35 %
181 km away, in 2024
First rain (1 mm or more) after it ended: 4.1 mm on 10 Jul.
Ayano-Maysky Rayon fire, June 2023
6,081 ha
10 days
FWI 27.3
Min. humidity 35 %
167 km away, in 2023
First rain (1 mm or more) after it ended: 4.2 mm on 8 Jul.
Ust-Maysky Ulus fire, August 2021
3,833 ha
10 days
FWI 26.0
Min. humidity 33 %
132 km away, in 2021
First rain (1 mm or more) after it ended: 1.3 mm on 18 Aug.
Ust-Maysky Ulus fire, June 2023
3,618 ha
8 days
FWI 22.5
Min. humidity 33 %
81 km away, in 2023
First rain (1 mm or more) after it ended: 8.1 mm on 8 Jul.
What happened to them
- 10 days
- median duration
- 8,123 ha
- median area
- 35 %
- went past 10,000 ha
- 4.1 mm
- rain at the end (median; 17 of 17 had it)
It burned an area similar to its twins (10,432 ha against a median of 8,123 ha) and lasted 14 days, against 10 days.
All of them had rain in the ten days after the end: the first rainy day brought a median of 4.1 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
4.0 mmfirst rain
14 Augthe day after it ended
44km/h · max. gust
It was considered over on 13 Aug, and on 14 Aug 4.0 mm fell. We do not know whether the rain or the firefighters put it out. Twins with rain when they ended: 17 of 17, with a median of 4.1 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 2017.
- 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 · 24 Jul 2023
After · 20 Aug 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 16 August 2023 the air beside the fire reached 920 µg/m³ of PM2.5. That day averaged 386: 26 times the WHO daily guideline (15).
PM2.5 peak920 µg/m³
Days over the guideline17 days
PM101,315 µg/m³
Optical depth8.34
WHO 15
29 Jul2 Aug6 Aug10 Aug14 Aug
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 · 1,753Every 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
- 4,462 haUst-Maysky Ulus29 June 2021 · 7 days · 6 km away
- 43,982 haUst-Maysky Ulus23 June 2021 · 23 days · 11 km away
- 3,444 haUst-Maysky Ulus8 August 2023 · 6 days · 17 km away
- 22,064 haUst-Maysky UlusJuly 2021 · 19 days · 24 km away
- 9,989 haUst-Maysky Ulus3 July 2018 · 15 days · 24 km away
- 30,181 haUst-Maysky Ulus5 August 2023 · 9 days · 34 km away
Frequently asked questions
- How long did the Ust-Maysky Ulus fire last?
- GWIS (Copernicus) dates it between 31 July 2023 and 13 August 2023: 14 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 10,432 hectares (104.3 km²). It is an estimate: official national figures may differ.
- Which municipalities burned?
- The fire only entered Ust-Maysky Ulus (10,422 ha, 0.1 %).
- What was the weather like?
- During the fire the temperature reached 29.7 °C, humidity dropped to 20 % and gusts hit 44 km/h. The fire danger index (FWI) reached 35, class High.
- Where does this data come from?
- From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Russia (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 2017 with a similar FWI, humidity and dry spell: 17. Their median duration was 10 days and their median area 8,123 ha; 35 % went past 10,000 ha. All of them had rain in the ten days after the end: the first rainy day brought a median of 4.1 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.
Emergency number: 112 · Emergency number and official warnings
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. 1,753 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 (Open Data Commons Open Database License 1.0). 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.