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Snell Fire, September 2018 Napa

Out · last detection 9 Sept 2018, 21:55 UTC

The fire started on 8 September 2018 in Napa, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 1,009 hectares, spread across a single county.

It is the 281th largest in California since 2016 (of 442 with a page). Number 317 in United States in 2018, of 511.

Burnt area
1,009ha
official perimeter (MTBS / NIFC)
Duration
1day
8 Sept 2018 – 8 Sept 2018
Municipalities hit
1
counties
Started on
8 Sept
2018
Heat detections
74
in a single hotspot: 70 MW
Danger at start
44
Very high · FWI index
Energy released
513MW
sum of detected power

Where it burned

9 Sept 2018
HOTSPOTS BY DAY 8 Sept8 Sept

How it evolved, day by day

89

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

The weather it burned in

34°high
34km/h · peak gust
13%lowest humidity

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

This area had burned before

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

What happened to each town

  1. Napa where it started
    1,014 ha reached on 8 Sept
    0.5 %

Burnt area inside each county, 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.

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)
8 Sept 34.2 °C 13 % 34 km/h 0.0 mm Very high 44
9 Sept after 34.3 °C 18 % 33 km/h 0.0 mm Very high 43
10 Sept after 34.9 °C 17 % 30 km/h 0.0 mm Very high 42
11 Sept after 33.1 °C 9 % 46 km/h 0.0 mm Extreme 53
12 Sept after 26.0 °C 21 % 39 km/h 0.0 mm Very high 44
13 Sept after 26.2 °C 26 % 34 km/h 0.0 mm High 36
14 Sept after 27.5 °C 21 % 29 km/h 0.0 mm High 36
15 Sept after 25.7 °C 23 % 38 km/h 0.0 mm Very high 39
16 Sept after 27.8 °C 24 % 29 km/h 0.0 mm High 34
17 Sept after 27.3 °C 28 % 30 km/h 0.0 mm High 34
18 Sept after 27.7 °C 27 % 26 km/h 0.0 mm High 32
19 Sept after 30.3 °C 21 % 26 km/h 0.0 mm High 33

Before and after, from space

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

Before · 1 Sept 2018
After · 15 Sept 2018

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 · 74Every 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 timeSatelliteFRP (MW)LatLon

Other fires nearby

All fires in United States ›

Frequently asked questions

How long did the Snell fire last?
It burned between 8 September 2018 and 8 September 2018: 1 day, according to the start date recorded by United States agencies (MTBS / NIFC) and the heat detections seen by satellite.
How much area did it burn?
The official perimeter published by United States agencies (MTBS / NIFC) is 1,009 hectares (10.1 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Napa (1,014 ha, 0.5 %).
What was the weather like?
During the fire the temperature reached 34.3 °C, humidity dropped to 13 % and gusts hit 34 km/h. The fire danger index (FWI) reached 44, class Very high.
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

Satellite cross-check

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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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.

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.