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.
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
model
21.6°C · 45% RH
High of 21.6 °C and minimum humidity of 45% on 12 October 2021; gusts of 18 km/h on 12 October 2021.
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
· reconstructedweather
Weather and FWI computed from the ERA5 reanalysis
· reconstructedofficial
Matched with the official ICNF record
Matches: 198 ha in the official record (records: 1).
A 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
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.
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 start5.5
Minimum humidity45 %
Days without rain6
this firechosen twinsrest of the area
Almost identicalSimilar
Outlines of the closest twins
This fire · Viana do Castelo fire, October 2021
198 ha1 dayFWI 5.5Min. humidity 45 %
Montalegre fire, March 2021
151 ha3 daysFWI 5.1Min. humidity 45 %77 km away, in 2021
First rain (1 mm or more) after it ended: 16.6 mm on 1 Apr.
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.
Drag the line to compare the same ground before the fire and after it.
↔
Before · 5 Oct 2021
After · 19 Oct 2021
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 · 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 peak21µg/m³
Days over the guideline0days
PM1029µg/m³
WHO 15
10 Oct12 Oct14 Oct
GoodFairModeratePoorVery poorExtremely 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 CSVTimes in UTC. Each detection is a 375 m pixel: a large fire yields hundreds per pass.
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.
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 errorHow 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.
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.