How long did the Ust-Maysky Ulus fire last?

GWIS (Copernicus) dates it between 24 July 2023 and 13 August 2023: 21 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 63,475 hectares (634.8 km²). It is an estimate: official national figures may differ.

Which municipalities burned?

The fire only entered Ust-Maysky Ulus (63,972 ha, 0.7 %).

What was the weather like?

During the fire the temperature reached 29.4 °C, humidity dropped to 25 % and gusts hit 40 km/h. The fire danger index (FWI) reached 27, 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.

RU · Russia · 2023-07-24 → 2023-08-13

Ust-Maysky Ulus fire, 24 July 2023 Ust-Maysky Ulus

Out · last detection 13 Aug 2023, 18:23 UTC

The fire started on 24 July 2023 in Ust-Maysky Ulus, Russia, and satellites saw it burning for 21 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 63,475 hectares from heat detections, spread across a single municipality.

It is the 61th largest in Sakha Republic since 2016 (of 1422 with a page). Number 4 in Russia in 2023, of 450.

Compare with…

Suggestions: Ust-Maysky Ulus · 2017 Ust-Maysky Ulus · 2021 Ust-Maysky Ulus · 2021 Ust-Maysky Ulus · 2021

Burnt area: 63,475ha; GWIS perimeter (Copernicus)
Duration: 21days; 24 Jul 2023 – 13 Aug 2023
Municipalities hit: 1; districts
Started on: 24 Jul; 2023
Heat detections: 10,154; in a single hotspot: 482 MW
Danger at start: 11; Low · FWI index
Average daily power: 3.8GW; detected power per day, on average

HOTSPOTS BY DAY 24 Jul13 Aug

Play back 13 Aug 2023

How it evolved, day by day

24 Jul 28 Jul 31 Jul 5 Aug 8 Aug 11 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

29°high

40km/h · peak gust

25%lowest humidity

It had gone one day without rain (1 mm or more) when it started. Rain came after the fire: 5.7 mm on 14 Aug.

This area had burned before

6% of the perimeter overlaps earlier fires recorded since 2016: 1,455 ha in 2017, 921 ha in 2018, 284 ha in 2020, 1,437 ha in 2021.

How big is it?

It burned the equivalent of 40% of the area of London (635 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

Ust-Maysky Ulus where it started

63,972 ha reached on 24 Jul

0.7 %

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)
24 Jul	28.4 °C	35 %	23 km/h	0.0 mm	Low 11
25 Jul	29.4 °C	37 %	23 km/h	0.0 mm	Moderate 12
26 Jul	27.2 °C	30 %	40 km/h	0.0 mm	Moderate 17
27 Jul	24.2 °C	25 %	36 km/h	0.0 mm	Moderate 19
28 Jul	24.2 °C	26 %	24 km/h	0.0 mm	Moderate 19
29 Jul	24.9 °C	27 %	31 km/h	0.2 mm	Moderate 20
30 Jul	24.8 °C	36 %	31 km/h	2.6 mm	Low 6
31 Jul	22.9 °C	37 %	27 km/h	0.3 mm	Moderate 12
1 Aug	15.8 °C	52 %	33 km/h	1.2 mm	Low 6
2 Aug	18.1 °C	51 %	24 km/h	1.2 mm	Very low 4
3 Aug	20.8 °C	42 %	25 km/h	0.4 mm	Low 10
4 Aug	25.3 °C	26 %	30 km/h	0.0 mm	Moderate 18
5 Aug	27.2 °C	25 %	30 km/h	0.0 mm	High 22
6 Aug	26.4 °C	29 %	30 km/h	0.0 mm	High 23
7 Aug	22.5 °C	28 %	36 km/h	0.0 mm	High 25
8 Aug	21.0 °C	37 %	32 km/h	0.0 mm	High 22
9 Aug	22.1 °C	31 %	27 km/h	0.0 mm	Moderate 21
10 Aug	23.7 °C	30 %	35 km/h	2.5 mm	Low 8
11 Aug	24.2 °C	50 %	34 km/h	1.2 mm	Low 8
12 Aug	26.7 °C	27 %	28 km/h	0.0 mm	Moderate 19
13 Aug	27.6 °C	26 %	40 km/h	0.0 mm	High 27
14 Aug after	18.9 °C	45 %	39 km/h	5.7 mm	Very low 3

Before and after, from space

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

↔

Before · 17 Jul 2023

After · 20 Aug 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 10 August 2023 the air beside the fire reached 725 µg/m³ of PM2.5. That day averaged 320: 21 times the WHO daily guideline (15).

PM2.5 peak725 µg/m³

Days over the guideline20 days

PM101,036 µg/m³

Optical depth9.41

WHO 15

2223242526272829303112345678910111213141516

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 · 10,154Every 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 Russia ›

Frequently asked questions

How long did the Ust-Maysky Ulus fire last?: GWIS (Copernicus) dates it between 24 July 2023 and 13 August 2023: 21 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 63,475 hectares (634.8 km²). It is an estimate: official national figures may differ.
Which municipalities burned?: The fire only entered Ust-Maysky Ulus (63,972 ha, 0.7 %).
What was the weather like?: During the fire the temperature reached 29.4 °C, humidity dropped to 25 % and gusts hit 40 km/h. The fire danger index (FWI) reached 27, 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.

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

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?

Your connection to the fire (optional) Email (optional)

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 112.

How we know this

Perimeter: GWIS (Copernicus), rebuilt from heat detections rather than mapped on imagery; 2 polygons grouped in this page.
Dates from the perimeter: the VIIRS detections inside it did not change them. 10,154 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 (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.

Where it burned