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Dem fire, October 2025 Arga (Baixo, Cima e São João), Montaria, Dem

Out · last measured on 30 Oct 2025

The fire started on 27 October 2025 in Dem, Portugal, and satellites saw it burning for 4 days. Copernicus mapped a burnt perimeter of 411 hectares from satellite imagery, spread across 3 municipalities.

Number 42 in Portugal in 2025, of 85.

We have the Copernicus perimeter for this fire, but not yet its hotspots: NASA publishes the yearly hotspot archive only once the year closes. The page picks it up automatically when it is available.

Burnt area
411ha
Copernicus perimeter
Duration
4days
27 Oct 2025 – 30 Oct 2025
Municipalities hit
3
freguesias
Started on
27 Oct
2025
Danger at start
0
Very low · FWI index
Natura 2000
97%
of the perimeter is protected land

Where it burned

The weather it burned in

16°high
64km/h · peak gust
48%lowest humidity

It had gone one day without rain (1 mm or more) when it started. Rain came after the fire: 57.6 mm on 31 Oct.

This area had burned before

98% of the perimeter overlaps earlier fires recorded since 2016: 399 ha in 2016, 364 ha in 2020, 11 ha in 2021. Part of it burned more than once, so the yearly figures add up to more than the 404 ha that had burned before.

What happened to each town

  1. Arga (Baixo, Cima e São João) 159 inhabitants · 3.6 km from the town
    161 ha
    5.2 %
  2. Montaria 450 inhabitants · 2.8 km from the town
    131 ha
    5.8 %
  3. Dem 309 inhabitants · 0.7 km from the town where it started
    119 ha
    18 %

Burnt area inside each municipality, from crossing the official perimeter with administrative boundaries. The distance is from the town centre to the nearest fire: staying a kilometre away does not mean it reached the houses.

What burned

  • Other natural land95 %
  • Scrub and transitional woodland5.2 %

Natura 2000 protected area affected: 97 %

Natura 2000 sites (European Environment Agency, 2024 release) crossed by the perimeter.

Land cover inside the perimeter according to Corine Land Cover, as reported by Copernicus.

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)
27 Oct 15.7 °C 48 % 20 km/h 0.0 mm Very low 0
28 Oct 13.6 °C 67 % 39 km/h 15.1 mm Very low 0
29 Oct 13.9 °C 80 % 37 km/h 14.0 mm Very low 0
30 Oct 13.3 °C 80 % 64 km/h 8.5 mm Very low 0
31 Oct after 14.0 °C 90 % 62 km/h 57.6 mm Very low 0

Before and after, from space

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

Before · 20 Oct 2025
After · 6 Nov 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 30 October 2025 the air beside the fire reached 11 µg/m³ of PM2.5, but no daily average passed the WHO guideline (15).

PM2.5 peak11 µg/m³
Days over the guideline0 days
PM1016 µg/m³
Optical depth0.23
2526272829303112
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

All fires in Portugal ›

Frequently asked questions

How long did the Dem fire last?
Copernicus dates it between 27 October 2025 and 30 October 2025: 4 days between the first and last image with fire.
How much area did it burn?
The perimeter Copernicus measured from satellite imagery is 411 hectares (4.1 km²). Official national figures may differ.
Which municipalities burned?
The fire entered 3 municipalities: Arga (Baixo, Cima e São João) (161 ha, 5.2 %); Montaria (131 ha, 5.8 %); Dem (119 ha, 18 %).
Did the fire reach a town?
The closest fire to a town centre came within 0.7 km of Dem. That is the distance to the perimeter or nearest hotspot; it does not mean it entered the houses.
What was the weather like?
During the fire the temperature reached 15.7 °C, humidity dropped to 48 % and gusts hit 64 km/h. The fire danger index (FWI) reached 0, class Very low.
Where does this data come from?
From the EFFIS (Copernicus) burnt perimeter, NASA FIRMS VIIRS hotspots and the administrative boundaries of Portugal (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

Satellite cross-check

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 112.

Where this data comes from

The perimeter and land cover come from the Copernicus European Forest Fire Information System (EFFIS), measured on MODIS and Sentinel-2 imagery and published under CC BY 4.0. 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 ADM3 (CC0 1.0 Universal (CC0 1.0) Public Domain Dedication). The area per municipality is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ slightly from each country’s official figure.