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Balsas fire, 4 September 2025 Balsas

Out · last detection 29 Sept 2025, 16:22 UTC

The fire started on 4 September 2025 in Balsas, Brazil, and satellites saw it burning for 26 days. Copernicus’s global GWIS system rebuilt a burnt perimeter of 10,919 hectares from heat detections, spread across a single municipality.

It is the 47th largest in Maranhão since 2016 (of 608 with a page). Number 109 in Brazil in 2025, of 714.

Compare with…

Suggestions: Balsas · 2025Balsas · 2026Tasso Fragoso · 2017Riachão · 2025

Burnt area
10,919ha
GWIS perimeter (Copernicus)
Duration
26days
4 Sept 2025 – 29 Sept 2025
Municipalities hit
1
municipalities
Started on
4 Sept
2025
Heat detections
269
in a single hotspot: 75 MW
Danger at start
56
Extreme · FWI index
Average daily power
89MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 4 Sept29 Sept
29 Sept 2025

How it evolved, day by day

4 Sept 2025 · 9 MW · 3 5 Sept 2025 · 8 MW · 5 6 Sept 2025 · 3 MW · 3 8 Sept 2025 · 180 MW · 5 9 Sept 2025 · 391 MW · 40 10 Sept 2025 · 105 MW · 33 11 Sept 2025 · 49 MW · 10 12 Sept 2025 · 124 MW · 12 14 Sept 2025 · 18 MW · 6 15 Sept 2025 · 226 MW · 40 16 Sept 2025 · 92 MW · 21 17 Sept 2025 · 418 MW · 44 18 Sept 2025 · 64 MW · 11 19 Sept 2025 · 6 MW · 1 21 Sept 2025 · 5 MW · 3 22 Sept 2025 · 53 MW · 11 23 Sept 2025 · 10 MW · 4 24 Sept 2025 · 82 MW · 10 25 Sept 2025 · 9 MW · 5 26 Sept 2025 · 2 MW · 1 29 Sept 2025 · 7 MW · 1
4 Sept 8 Sept 11 Sept 15 Sept 17 Sept 18 Sept 22 Sept 25 Sept

Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.

The weather it burned in

39°high
48km/h · peak gust
12%lowest humidity

It had gone more than two months without rain (1 mm or more) when it started.

This area had burned before

51% of the perimeter overlaps earlier fires recorded since 2016: 927 ha in 2016, 2,785 ha in 2017, 398 ha in 2019, 1,396 ha in 2020, 824 ha in 2022, 889 ha in 2023, 381 ha in 2024. Part of it burned more than once, so the yearly figures add up to more than the 5,601 ha that had burned before.

How big is it?

10 km
It burned the equivalent of 6.9% of the area of London (109 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. Balsas 101,767 inhabitants where it started
    10,977 ha reached on 4 Sept
    0.8 %

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 area0.13 ha
Residents< 20

Inside the perimeter there were about 0.13 hectares of 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)
4 Sept 36.3 °C 21 % 48 km/h 0.0 mm Extreme 56
5 Sept 36.2 °C 19 % 43 km/h 0.0 mm Extreme 55
6 Sept 37.1 °C 16 % 40 km/h 0.0 mm Extreme 53
7 Sept 38.4 °C 14 % 39 km/h 0.0 mm Extreme 53
8 Sept 37.9 °C 16 % 41 km/h 0.0 mm Extreme 57
9 Sept 37.7 °C 13 % 40 km/h 0.0 mm Extreme 54
10 Sept 39.2 °C 12 % 36 km/h 0.0 mm Extreme 54
11 Sept 39.0 °C 16 % 34 km/h 0.0 mm Extreme 53
12 Sept 37.3 °C 16 % 45 km/h 0.0 mm Extreme 60
13 Sept 35.8 °C 22 % 33 km/h 0.0 mm Very high 48
14 Sept 37.9 °C 17 % 41 km/h 0.0 mm Extreme 52
15 Sept 39.3 °C 14 % 38 km/h 0.0 mm Extreme 55
16 Sept 38.2 °C 18 % 34 km/h 0.0 mm Extreme 52
17 Sept 38.8 °C 19 % 41 km/h 0.0 mm Extreme 57
18 Sept 37.7 °C 21 % 39 km/h 0.0 mm Extreme 54
19 Sept 38.1 °C 21 % 30 km/h 0.0 mm Very high 49
20 Sept 37.0 °C 20 % 37 km/h 0.0 mm Extreme 53
21 Sept 35.9 °C 25 % 37 km/h 0.3 mm Very high 50
22 Sept 35.5 °C 35 % 29 km/h 0.8 mm High 32
23 Sept 35.1 °C 37 % 31 km/h 0.1 mm High 32
24 Sept 36.9 °C 30 % 31 km/h 0.0 mm High 35
25 Sept 37.9 °C 21 % 38 km/h 0.0 mm Very high 46
26 Sept 36.7 °C 24 % 37 km/h 0.0 mm Very high 47
27 Sept 35.6 °C 23 % 39 km/h 0.0 mm Very high 47
28 Sept 37.8 °C 17 % 43 km/h 0.0 mm Extreme 53
29 Sept 38.0 °C 21 % 36 km/h 0.0 mm Extreme 51
30 Sept after 38.6 °C 18 % 43 km/h 0.0 mm Extreme 52
1 Oct after 38.4 °C 19 % 35 km/h 0.0 mm Extreme 51
2 Oct after 38.6 °C 18 % 35 km/h 0.0 mm Extreme 50
3 Oct after 37.7 °C 18 % 36 km/h 0.0 mm Extreme 51
4 Oct after 37.2 °C 19 % 48 km/h 0.0 mm Extreme 58
5 Oct after 37.7 °C 18 % 47 km/h 0.0 mm Extreme 57
6 Oct after 38.0 °C 27 % 40 km/h 0.0 mm Very high 50
7 Oct after 37.3 °C 25 % 38 km/h 0.1 mm Very high 46
8 Oct after 38.1 °C 26 % 39 km/h 0.0 mm Very high 46
9 Oct after 34.3 °C 37 % 26 km/h 0.3 mm High 36

Before and after, from space

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

Before · 28 Aug 2025
After · 6 Oct 2025

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 11 September 2025 the air beside the fire reached 33 µg/m³ of PM2.5. That day averaged 21: 1.4 times the WHO daily guideline (15).

PM2.5 peak33 µg/m³
Days over the guideline3 days
PM1033 µg/m³
Optical depth0.44
234567891011121314151617181920212223242526272829
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 · 269Every 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 Brazil ›

Frequently asked questions

How long did the Balsas fire last?
According to the heat detections seen by satellite inside the perimeter, it burned from 4 September 2025 to 29 September 2025 (26 days). The perimeter dates it from 8 September 2025 to 26 September 2025.
How much area did it burn?
The perimeter GWIS (Copernicus) rebuilt from heat detections is 10,919 hectares (109.2 km²). It is an estimate: official national figures may differ.
Which municipalities burned?
The fire only entered Balsas (10,977 ha, 0.8 %).
What was the weather like?
During the fire the temperature reached 39.3 °C, humidity dropped to 12 % and gusts hit 48 km/h. The fire danger index (FWI) reached 60, class Extreme.
Where does this data come from?
From the GWIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Brazil (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: 193 · 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: 26 September 2025 → 29 September 2025.
  2. Start date: 8 September 2025 → 4 September 2025.

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 193.

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 8 September 2025 to 26 September 2025. 269 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.