How long did the Nuns Fire last?

The official perimeter only gives the start date (9 October 2017). The end comes from the heat detections inside the perimeter: it burned until 18 October 2017 (10 days from 9 October 2017), the last day with detections before more than 10 days in a row without any, so it is approximate.

How much area did it burn?

The official perimeter published by United States agencies (MTBS / NIFC) is 23,002 hectares (230.0 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 2 counties: Sonoma (14,856 ha, 3.6 %); Napa (8,143 ha, 4.0 %).

What was the weather like?

During the fire the temperature reached 27.2 °C, humidity dropped to 9 % and gusts hit 62 km/h. The fire danger index (FWI) reached 55, class Extreme.

Where does this data come from?

From the official burnt perimeter of United States agencies (MTBS / NIFC, public domain), NASA FIRMS VIIRS hotspots and the administrative boundaries of United States. It is not an official report.

US · United States · 2017-10-09 → 2017-10-18

Nuns Fire, October 2017 Sonoma, Napa

Out · last detection 18 Oct 2017, 10:46 UTC

The fire started on 9 October 2017 in Sonoma, United States, and satellites saw it burning for 10 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 23,002 hectares, spread across 2 counties.

It is the 52th largest in California since 2016 (of 442 with a page). Number 28 in United States in 2017, of 619.

Compare with…

Suggestions: Glass · 2020 Atlas · 2017 Tubbs · 2017 Pickett · 2025

Burnt area: 23,002ha; official perimeter (MTBS / NIFC)
Duration: ≈ 10days; 9 Oct 2017 – 18 Oct 2017
Counties hit: 2; counties
Started on: 9 Oct; 2017
Heat detections: 2,020; in a single hotspot: 507 MW
Danger at start: 55; Extreme · FWI index
Average daily power: 2.7GW; detected power per day, on average

HOTSPOTS BY DAY 9 Oct18 Oct

Play back 18 Oct 2017

How it evolved, day by day

9 Oct 11 Oct 13 Oct 15 Oct 17 Oct

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

The weather it burned in

27°high

62km/h · peak gust

9%lowest humidity

It had gone more than two months without rain (1 mm or more) when it started. Rain came after the fire: 3.1 mm on 19 Oct.

This area had burned before

No earlier perimeters overlap this fire since 2016, when the satellite record begins.

How big is it?

It burned the equivalent of 15% of the area of London (230 km² against 1,583 km²).

London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).

This compares size, not location: both shapes are at the same scale, north up, centred on each other.

What happened to each county

Sonoma where it started

14,856 ha reached on 9 Oct

3.6 %
Napa

8,143 ha reached on 9 Oct

4.0 %

Burnt area inside each county, 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.

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)
9 Oct	25.8 °C	9 %	62 km/h	0.0 mm	Extreme 55
10 Oct	24.2 °C	19 %	31 km/h	0.0 mm	Very high 39
11 Oct	21.6 °C	14 %	35 km/h	0.0 mm	Very high 40
12 Oct	22.3 °C	16 %	27 km/h	0.0 mm	Very high 38
13 Oct	23.1 °C	22 %	29 km/h	0.0 mm	High 34
14 Oct	24.9 °C	12 %	33 km/h	0.0 mm	High 36
15 Oct	26.5 °C	9 %	37 km/h	0.0 mm	Very high 45
16 Oct	27.2 °C	9 %	22 km/h	0.0 mm	Very high 39
17 Oct	25.4 °C	16 %	24 km/h	0.0 mm	Very high 42
18 Oct	20.5 °C	34 %	35 km/h	0.0 mm	High 33
19 Oct after	16.9 °C	63 %	45 km/h	3.1 mm	Low 6

Before and after, from space

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

↔

Before · 2 Oct 2017

After · 25 Oct 2017

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.

Detections table · 2,020Every 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 United States ›

Frequently asked questions

How long did the Nuns Fire last?: The official perimeter only gives the start date (9 October 2017). The end comes from the heat detections inside the perimeter: it burned until 18 October 2017 (10 days from 9 October 2017), the last day with detections before more than 10 days in a row without any, so it is approximate.
How much area did it burn?: The official perimeter published by United States agencies (MTBS / NIFC) is 23,002 hectares (230.0 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 2 counties: Sonoma (14,856 ha, 3.6 %); Napa (8,143 ha, 4.0 %).
What was the weather like?: During the fire the temperature reached 27.2 °C, humidity dropped to 9 % and gusts hit 62 km/h. The fire danger index (FWI) reached 55, class Extreme.
Where does this data come from?: From the official burnt perimeter of United States agencies (MTBS / NIFC, public domain), NASA FIRMS VIIRS hotspots and the administrative boundaries of United States. 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: 911 · Emergency number and official warnings ›

Satellite cross-check

NASA FIRMS ↗
NIFC · Fire maps ↗

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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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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What really happened?

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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 911.

How we know this

Perimeter: MTBS (US Geological Survey and US Forest Service), official.
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. 2,020 Suomi-NPP VIIRS detections on those dates.
We have not matched this page with any official record.
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 is official and in the public domain. For past years it comes from MTBS (Monitoring Trends in Burn Severity), run by the U.S. Geological Survey and the USDA Forest Service, which map it on Landsat and Sentinel-2 imagery. For the current and last year it comes from WFIGS at the National Interagency Fire Center (NIFC): incident perimeters mapped by fire crews, aircraft and imagery. Heat detections come from the VIIRS sensors aboard Suomi-NPP and NOAA-20, distributed by NASA FIRMS at 375 m resolution. County boundaries come from geoBoundaries ADM2 (Public Domain). The area per county is computed by WorldFires by crossing the perimeter with those boundaries, so it may differ slightly from official figures.

Where it burned