How long did the Nelas fire last?

Copernicus dates it between 23 August 2023 and 24 August 2023: 2 days between the first and last image with fire. According to ICNF, it was detected on 23 August 2023 at 12:24 and declared extinguished on 25 August 2023.

How much area did it burn?

The perimeter Copernicus measured from satellite imagery is 1,110 hectares (11.1 km²). Official national figures may differ.

Which municipalities burned?

The fire entered 2 municipalities: Senhorim (1,030 ha, 33 %); Nelas (82 ha, 3.7 %).

Did the fire reach a town?

The closest fire to a town centre came within 0.1 km of Senhorim. 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 39.9 °C, humidity dropped to 15 % and gusts hit 48 km/h. The fire danger index (FWI) reached 66, class Extreme.

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 · 2023-08-23 → 2023-08-24

Nelas fire, August 2023 Senhorim, Nelas

Out · last detection 24 Aug 2023, 03:10 UTC

The fire started on 23 August 2023 in Senhorim, Portugal, and satellites saw it burning for 2 days. Copernicus mapped a burnt perimeter of 1,110 hectares from satellite imagery, spread across 2 municipalities. According to ICNF, it was detected on 23 August 2023 at 12:24 and declared extinguished on 25 August 2023.

Number 5 in Portugal in 2023, of 38.

Burnt area: 1,110ha; Copernicus perimeter
Duration: 2days; 23 Aug 2023 – 24 Aug 2023
Municipalities hit: 2; freguesias
Started on: 23 Aug; 2023
Heat detections: 26; in a single hotspot: 372 MW
Danger at start: 66; Extreme · FWI index
Energy released: 2.3GW; sum of detected power

Play back 24 Aug 2023

HOTSPOTS BY DAY 23 Aug24 Aug

How it evolved, day by day

2324

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

The weather it burned in

40°high

48km/h · peak gust

15%lowest humidity

It had gone 20 days without rain (1 mm or more) when it started. Rain came after the fire: 7.2 mm on 2 Sept.

This area had burned before

93% of the perimeter overlaps earlier fires recorded since 2016: 305 ha in 2016, 830 ha in 2017, 7 ha in 2022. Part of it burned more than once, so the yearly figures add up to more than the 1,027 ha that had burned before.

What happened to each town

Senhorim 1,019 inhabitants · 0.1 km from the town where it started

1,030 ha reached on 23 Aug

33 %
Nelas 4,636 inhabitants · 0.8 km from the town

82 ha reached on 23 Aug

3.7 %

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

Scrub and transitional woodland45 %
Other natural land27 %
Coniferous forest15 %
Agricultural areas13 %

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

Official record

According to ICNF, this fire started on 23 August 2023 and burned 1,051 ha (the satellite measured 1,110 ha).

Nelas Nelas 23 August 2023 · 12:24 1,051 ha · extinguished on 25 August 2023 · cause: arson

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)
23 Aug	39.9 °C	15 %	48 km/h	0.0 mm	Extreme 66
24 Aug	33.9 °C	26 %	39 km/h	0.0 mm	Very high 50
25 Aug after	31.1 °C	30 %	42 km/h	0.0 mm	Very high 48
26 Aug after	26.5 °C	28 %	47 km/h	0.0 mm	Very high 50
27 Aug after	26.6 °C	24 %	37 km/h	0.0 mm	Very high 43
28 Aug after	28.7 °C	30 %	40 km/h	0.0 mm	Very high 44
29 Aug after	28.9 °C	29 %	42 km/h	0.0 mm	Very high 45
30 Aug after	30.0 °C	17 %	30 km/h	0.0 mm	Very high 43
31 Aug after	30.6 °C	24 %	37 km/h	0.0 mm	Very high 47
1 Sept after	27.2 °C	37 %	37 km/h	0.0 mm	High 37
2 Sept after	22.8 °C	51 %	28 km/h	7.2 mm	Very low 4

Before and after, from space

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

↔

Before · 16 Aug 2023

After · 31 Aug 2023

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 24 August 2023 the air beside the fire reached 22 µg/m³ of PM2.5. That day averaged 16: 1.1 times the WHO daily guideline (15).

PM2.5 peak22 µg/m³

Days over the guideline1 day

PM1046 µg/m³

Optical depth0.25

WHO 15

21222324252627

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 · 26Every 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 Nelas fire last?: Copernicus dates it between 23 August 2023 and 24 August 2023: 2 days between the first and last image with fire. According to ICNF, it was detected on 23 August 2023 at 12:24 and declared extinguished on 25 August 2023.
How much area did it burn?: The perimeter Copernicus measured from satellite imagery is 1,110 hectares (11.1 km²). Official national figures may differ.
Which municipalities burned?: The fire entered 2 municipalities: Senhorim (1,030 ha, 33 %); Nelas (82 ha, 3.7 %).
Did the fire reach a town?: The closest fire to a town centre came within 0.1 km of Senhorim. 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 39.9 °C, humidity dropped to 15 % and gusts hit 48 km/h. The fire danger index (FWI) reached 66, class Extreme.
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

NASA FIRMS ↗
EFFIS · Copernicus ↗

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.

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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