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PT · Portugal ·

Viana do Castelo fire, October 2021 Montaria, Arga (Baixo, Cima e São João)

Out · last detection 12 Oct 2021, 02:37 UTC

The fire started on 12 October 2021 in Montaria, Portugal, and satellites saw it burning for 1 day. Copernicus mapped a burnt perimeter of 198 hectares from satellite imagery, spread across 2 freguesias. According to ICNF, it was detected on 11 October 2021 at 20:08 and declared extinguished on 12 October 2021.

Number 14 in Portugal in 2021, of 30.

The power measured by the satellite is low (15.9 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.

Burnt area
198ha
Copernicus perimeter
Duration
1day
12 Oct 2021 – 12 Oct 2021
Freguesias hit
2
freguesias
Started on
12 Oct
2021
Heat detections
11
in a single hotspot: 16 MW
Danger at start
6
Low · FWI index
Average daily power
97MW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 12 Oct12 Oct

How it evolved, day by day

12 Oct 2021 · 97 MW · 11

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

The weather it burned in

22°high
18km/h · peak gust
45%lowest humidity

It had gone 6 days without rain (1 mm or more) when it started. Rain came after the fire: 10.5 mm on 16 Oct.

This area had burned before

100% of the perimeter overlaps earlier fires recorded since 2016: 198 ha in 2016, 2 ha in 2020.

What happened to each freguesia

  1. Montaria 450 inhabitants · 1.9 km from the centre where it started
    198 ha reached on 12 Oct
    8.8 %
  2. Arga (Baixo, Cima e São João) 159 inhabitants · 4.1 km from the centre
    0 ha
    0.0 %

Burnt area inside each freguesia, from crossing the official 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.

What burned

  • Other natural land99 %
  • Scrub and transitional woodland1.0 %

Natura 2000 protected area affected: 100 %

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.

Official record

According to ICNF, this fire started on 11 October 2021 and burned 198 ha (the satellite measured 198 ha).

ICNF (Instituto da Conservação da Natureza e das Florestas). This is the agency’s operational record: its figures may be revised when the year’s statistics are closed.

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)
12 Oct 21.6 °C 45 % 18 km/h 0.0 mm Low 6
13 Oct after 20.8 °C 38 % 21 km/h 0.0 mm Low 8
14 Oct after 19.2 °C 51 % 16 km/h 0.0 mm Low 7
15 Oct after 17.6 °C 68 % 24 km/h 0.0 mm Low 6
16 Oct after 15.7 °C 82 % 39 km/h 10.5 mm Very low 4

Its twins: fires that started in the same weather

It started with an FWI of 5.5, a minimum humidity of 45% and 6 days without rain. Fires in the area that started in weather like this since 2016: 16.

FWI at the start 5.5
Minimum humidity 45 %
Days without rain 6
this fire chosen twins rest of the area
Almost identicalSimilar

Outlines of the closest twins

Montalegre fire, March 2021
151 ha 3 days FWI 5.1 Min. humidity 45 % 77 km away, in 2021

First rain (1 mm or more) after it ended: 16.6 mm on 1 Apr.

What happened to them

2 days
median duration
132 ha
median area
0 %
went past 1,000 ha
3.8 mm
rain at the end (median; 12 of 16 had it)

It burned an area similar to its twins (198 ha against a median of 132 ha) and lasted 1 day, against 2 days.

In 4 of 16, 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 3.8 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

10.5 mmfirst rain
16 Oct4 days after it ended
18km/h · max. gust

It was considered over on 12 Oct, and on 16 Oct 10.5 mm fell. We do not know whether the rain or the firefighters put it out. Twins with rain when they ended: 12 of 16, with a median of 3.8 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.

How we calculate it

Before and after, from space

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

Before · 5 Oct 2021
After · 19 Oct 2021

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 15 October 2021 the air beside the fire reached 21 µg/m³ of PM2.5, but no daily average passed the WHO guideline (15).

PM2.5 peak21 µg/m³
Days over the guideline0 days
PM1029 µg/m³
10 Oct12 Oct14 Oct
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 · 11Every 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 Portugal

Frequently asked questions

How long did the Viana do Castelo fire last?
Copernicus dates it between 12 October 2021 and 12 October 2021: 1 day between the first and last image with fire. According to ICNF, it was detected on 11 October 2021 at 20:08 and declared extinguished on 12 October 2021.
How much area did it burn?
The perimeter Copernicus measured from satellite imagery is 198 hectares (2.0 km²). Official national figures may differ.
Which freguesias burned?
The fire entered 2 freguesias: Montaria (198 ha, 8.8 %); Arga (Baixo, Cima e São João) (0 ha, 0.0 %).
Did the fire reach a town?
The fire started in Montaria and came within 1.9 km of its centre. That is the distance from the perimeter, or the nearest hotspot, to the point marking the centre; it does not mean it entered the houses.
What was the weather like?
During the fire the temperature reached 21.6 °C, humidity dropped to 45 % and gusts hit 18 km/h. The fire danger index (FWI) reached 6, class 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.
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: 16. Their median duration was 2 days and their median area 132 ha; 0 % went past 1,000 ha. In 4 of 16, 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 3.8 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.

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
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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: EFFIS (Copernicus), mapped on satellite imagery.
  • Dates from the perimeter: the VIIRS detections inside it did not change them. 11 Suomi-NPP VIIRS detections on those dates.
  • Compared with ICNF: 198 official ha against 198 ha of perimeter; they agree within 25%.
  • Weather: Copernicus ERA5 reanalysis at the fire location, in cells of about 25 km.

How we build fire pages: methodology

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. Freguesia boundaries come from geoBoundaries ADM3 (CC0 1.0 Universal (CC0 1.0) Public Domain Dedication). The area per freguesia is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ slightly from each country’s official figure.