How long did the Santo Tirso fire last?

The official perimeter only gives the start date (17 August 2026). The end comes from the heat detections inside the perimeter: it burned until 19 August 2026 (3 days from 17 August 2026), the last day with detections before more than 10 days in a row without any, so it is approximate. According to ICNF, it was detected on 17 August 2026 at 17:40 and declared extinguished on 20 August 2026.

How much area did it burn?

The perimeter Copernicus measured from satellite imagery is 326 hectares (3.3 km²). Official national figures may differ.

Did the fire reach a town?

The fire came within 0.6 km of the centre of Negrelos (São Mamede), the closest of the areas it touched. 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 33.0 °C, humidity dropped to 36 % and gusts hit 34 km/h. The fire danger index (FWI) reached 26, class High.

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.

PT · Portugal · 2026-08-17 → 2026-08-19

Santo Tirso fire, August 2026 Monte Córdova, Santo Tirso, Couto (Santa Cristina e São Miguel) e Burgães, Negrelos (São Mamede)

Out · last detection 19 Aug 2026, 13:46 UTC

The fire started on 17 August 2026 in Santo Tirso, Couto (Santa Cristina e São Miguel) e Burgães, Portugal, and satellites saw it burning for 3 days. Copernicus mapped a burnt perimeter of 326 hectares from satellite imagery, spread across 4 municipalities. According to ICNF, it was detected on 17 August 2026 at 17:40 and declared extinguished on 20 August 2026.

Number 26 in Portugal in 2026, of 87.

The power measured by the satellite is low (18.3 MW in the strongest hotspot), more typical of grass or stubble burning, or a slow surface fire, than of a large crown fire.

Compare with…

Suggestions: Santo Tirso · 2016 Aguiar de Sousa · 2024 Celorico de Basto · 2024 Vieira do Minho · 2016

Burnt area: 326ha; Copernicus perimeter
Duration: ≈ 3days; 17 Aug 2026 – 19 Aug 2026
Municipalities hit: 4; freguesias
Started on: 17 Aug; 2026
Heat detections: 37; in a single hotspot: 18 MW
Danger at start: 26; High · FWI index
Average daily power: 98MW; detected power per day, on average

HOTSPOTS BY DAY 17 Aug19 Aug

Play back 19 Aug 2026

How it evolved, day by day

18 Aug 19 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

33°high

34km/h · peak gust

36%lowest humidity

It had gone 12 days without rain (1 mm or more) when it started. Rain came after the fire: 1.5 mm on 20 Aug.

This area had burned before

46% of the perimeter overlaps earlier fires recorded since 2016: 149 ha in 2016, 2 ha in 2021, 18 ha in 2023, 1 ha in 2024. Part of it burned more than once, so the yearly figures add up to more than the 150 ha that had burned before.

149 ha Santo Tirso fire, August 2016 154 ha in total; the hectares shown are those it shares with this fire

What happened to each town

Monte Córdova 3,850 inhabitants · 1.0 km from the centre

110 ha reached on 18 Aug

6.5 %
Santo Tirso, Couto (Santa Cristina e São Miguel) e Burgães 20,595 inhabitants · 4.6 km from the centre where it started

98 ha reached on 18 Aug

3.9 %
Negrelos (São Mamede) 3,755 inhabitants · 0.6 km from the centre

78 ha reached on 18 Aug

13 %
Rebordões 3,130 inhabitants · 1.3 km from the centre

40 ha reached on 18 Aug

9.5 %

Burnt area inside each municipality, 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

Mixed forest49 %
Scrub and transitional woodland48 %
Agricultural areas2.1 %
Artificial surfaces0.9 %

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

People and buildings inside the perimeter

GHSL 2025

Built-up area2.3 ha

Residents≈ 70

Inside the perimeter there were about 2.3 hectares of built-up land and about 70 residents (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

Official record

According to ICNF, this fire started on 17 August 2026 and burned 371 ha (the satellite measured 326 ha).

Santo Tirso Rebordões 17 August 2026 · 17:40 371 ha · extinguished on 20 August 2026 · cause: unknown

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)
17 Aug	33.0 °C	36 %	25 km/h	0.0 mm	High 26
18 Aug	30.8 °C	47 %	34 km/h	0.0 mm	High 26
19 Aug	24.1 °C	68 %	28 km/h	0.0 mm	Moderate 16
20 Aug after	22.0 °C	67 %	40 km/h	1.5 mm	Low 10

Before and after, from space

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

↔

Before · 10 Aug 2026

After · 26 Aug 2026

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 20 August 2026 the air beside the fire reached 178 µg/m³ of PM2.5. That day averaged 57: 3.8 times the WHO daily guideline (15).

PM2.5 peak178 µg/m³

Days over the guideline3 days

PM10193 µg/m³

Optical depth0.83

WHO 15

151617181920

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 · 37Every 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 Portugal ›

Frequently asked questions

How long did the Santo Tirso fire last?: The official perimeter only gives the start date (17 August 2026). The end comes from the heat detections inside the perimeter: it burned until 19 August 2026 (3 days from 17 August 2026), the last day with detections before more than 10 days in a row without any, so it is approximate. According to ICNF, it was detected on 17 August 2026 at 17:40 and declared extinguished on 20 August 2026.
How much area did it burn?: The perimeter Copernicus measured from satellite imagery is 326 hectares (3.3 km²). Official national figures may differ.
Which municipalities burned?: The fire entered 4 municipalities: Monte Córdova (110 ha, 6.5 %); Santo Tirso, Couto (Santa Cristina e São Miguel) e Burgães (98 ha, 3.9 %); Negrelos (São Mamede) (78 ha, 13 %); Rebordões (40 ha, 9.5 %).
Did the fire reach a town?: The fire came within 0.6 km of the centre of Negrelos (São Mamede), the closest of the areas it touched. 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 33.0 °C, humidity dropped to 36 % and gusts hit 34 km/h. The fire danger index (FWI) reached 26, class High.
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 · Emergency number and official warnings ›

Satellite cross-check

NASA FIRMS ↗
EFFIS · 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

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How we know this

Perimeter: EFFIS (Copernicus), mapped on satellite imagery.
The official perimeter has no end date: the end is the last day with VIIRS detections inside the perimeter before a gap of more than 10 days (150 days at most), so it is approximate. 37 Suomi-NPP VIIRS detections on those dates.
Compared with ICNF: 371 official ha against 326 ha of perimeter; they agree within 25%.
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 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.

Where it burned