How long did the Glass Fire last?

The official perimeter only gives the start date (27 September 2020). The end comes from the heat detections inside the perimeter: it burned until 23 October 2020 (27 days from 27 September 2020), 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 27,507 hectares (275.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire entered 2 counties: Napa (16,789 ha, 8.2 %); Sonoma (10,771 ha, 2.6 %).

What was the weather like?

During the fire the temperature reached 37.4 °C, humidity dropped to 2 % and gusts hit 48 km/h. The fire danger index (FWI) reached 63, 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 · 2020-09-27 → 2020-10-23

Glass Fire, September 2020 Napa, Sonoma

Out · last detection 23 Oct 2020, 10:02 UTC

The fire started on 27 September 2020 in Napa, United States, and satellites saw it burning for 27 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 27,507 hectares, spread across 2 counties.

It is the 43th largest in California since 2016 (of 442 with a page). Number 35 in United States in 2020, of 441.

Compare with…

Suggestions: Nuns · 2017 Tubbs · 2017 Hennessey · 2020 Kincade · 2019

Burnt area: 27,507ha; official perimeter (MTBS / NIFC)
Duration: ≈ 27days; 27 Sept 2020 – 23 Oct 2020
Counties hit: 2; counties
Started on: 27 Sept; 2020
Heat detections: 2,425; in a single hotspot: 767 MW
Danger at start: 56; Extreme · FWI index
Average daily power: 3.5GW; detected power per day, on average

HOTSPOTS BY DAY 27 Sept23 Oct

Play back 23 Oct 2020

How it evolved, day by day

27 Sept 28 Sept 29 Sept 1 Oct 3 Oct 5 Oct 7 Oct 23 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

37°high

48km/h · peak gust

2%lowest humidity

It had gone more than two months without rain (1 mm or more) when it started.

This area had burned before

9% of the perimeter overlaps earlier fires recorded since 2016: 2,489 ha in 2017.

How big is it?

It burned the equivalent of 17% of the area of London (275 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

Napa where it started

16,789 ha reached on 27 Sept

8.2 %
Sonoma

10,771 ha reached on 28 Sept

2.6 %

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.

People and buildings inside the perimeter

GHSL 2020

Built-up area122 ha

Residents≈ 3,800

Inside the perimeter there were about 122 hectares of built-up land and about 3,800 residents (GHSL 2020, 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.

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

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	Danger (FWI)
27 Sept	36.3 °C	9 %	48 km/h	Extreme 56
28 Sept	37.4 °C	2 %	42 km/h	Extreme 63
29 Sept	33.2 °C	15 %	24 km/h	Very high 45
30 Sept	37.3 °C	15 %	23 km/h	Very high 47
1 Oct	36.6 °C	12 %	26 km/h	Very high 48
2 Oct	35.8 °C	12 %	32 km/h	Extreme 51
3 Oct	37.1 °C	8 %	40 km/h	Extreme 54
4 Oct	33.0 °C	9 %	34 km/h	Extreme 54
5 Oct	33.0 °C	14 %	21 km/h	Very high 45
6 Oct	31.5 °C	18 %	26 km/h	Very high 43
7 Oct	26.8 °C	26 %	31 km/h	Very high 38
8 Oct	23.0 °C	41 %	36 km/h	High 29
9 Oct	22.3 °C	48 %	30 km/h	High 23
10 Oct	21.8 °C	66 %	37 km/h	Moderate 19
11 Oct	28.8 °C	17 %	27 km/h	High 33
12 Oct	31.0 °C	19 %	21 km/h	High 34
13 Oct	33.3 °C	19 %	26 km/h	High 37
14 Oct	36.1 °C	8 %	31 km/h	Very high 49
15 Oct	36.0 °C	7 %	44 km/h	Extreme 57
16 Oct	36.0 °C	3 %	39 km/h	Extreme 59
17 Oct	35.2 °C	9 %	24 km/h	Extreme 53
18 Oct	32.3 °C	17 %	27 km/h	Very high 45
19 Oct	30.4 °C	21 %	22 km/h	Very high 39
20 Oct	32.2 °C	17 %	26 km/h	Very high 44
21 Oct	31.3 °C	19 %	26 km/h	Very high 42
22 Oct	27.3 °C	5 %	32 km/h	Very high 47
23 Oct	25.1 °C	20 %	29 km/h	Very high 42
24 Oct after	21.2 °C	39 %	31 km/h	High 30
25 Oct after	22.9 °C	2 %	67 km/h	Extreme 64
26 Oct after	24.2 °C	2 %	73 km/h	Very extreme 70
27 Oct after	29.0 °C	12 %	40 km/h	Extreme 52
28 Oct after	25.9 °C	14 %	22 km/h	Very high 41
29 Oct after	26.6 °C	12 %	17 km/h	Very high 41
30 Oct after	25.8 °C	21 %	22 km/h	High 38
31 Oct after	27.4 °C	17 %	16 km/h	High 37
1 Nov after	26.9 °C	14 %	26 km/h	Very high 39
2 Nov after	28.1 °C	14 %	16 km/h	Very high 39

Before and after, from space

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

↔

Before · 20 Sept 2020

After · 30 Oct 2020

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 · 2,425Every 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 Glass Fire last?: The official perimeter only gives the start date (27 September 2020). The end comes from the heat detections inside the perimeter: it burned until 23 October 2020 (27 days from 27 September 2020), 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 27,507 hectares (275.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire entered 2 counties: Napa (16,789 ha, 8.2 %); Sonoma (10,771 ha, 2.6 %).
What was the weather like?: During the fire the temperature reached 37.4 °C, humidity dropped to 2 % and gusts hit 48 km/h. The fire danger index (FWI) reached 63, 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

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

What do you think is wrong?

Dates or duration Place or towns Burned area Name It was not a wildfire Same fire as another page Something else

What really happened?

Your connection to the fire (optional) Email (optional)

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. 2,425 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.
Built-up area and population come from the JRC Global Human Settlement Layer (epoch 2020, 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 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