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Long Valley Fire, July 2017 Washoe, Lassen

Out · last detection 17 Jul 2017, 09:48 UTC

The fire started on 11 July 2017 in Washoe, United States, and satellites saw it burning for 7 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 32,578 hectares, spread across 2 counties.

It is the 11th largest in Nevada since 2016 (of 237 with a page). Number 20 in United States in 2017, of 619.

Compare with…

Suggestions: Sage · 2016Tule · 2016Anderson · 2016Bug · 2026

Burnt area
32,578ha
official perimeter (MTBS / NIFC)
Duration
≈ 7days
11 Jul 2017 – 17 Jul 2017
Counties hit
2
counties
Started on
11 Jul
2017
Heat detections
664
in a single hotspot: 406 MW
Danger at start
58
Extreme · FWI index
Average daily power
1.9GW
detected power per day, on average

Where it burned

HOTSPOTS BY DAY 11 Jul17 Jul
17 Jul 2017

How it evolved, day by day

11 Jul 2017 · 631 MW · 4 12 Jul 2017 · 1,603 MW · 94 13 Jul 2017 · 613 MW · 83 14 Jul 2017 · 1,277 MW · 88 15 Jul 2017 · 4,408 MW · 179 16 Jul 2017 · 4,532 MW · 185 17 Jul 2017 · 36 MW · 31
11 Jul 12 Jul 13 Jul 14 Jul 15 Jul 16 Jul 17 Jul

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

The weather it burned in

35°high
57km/h · peak gust
7%lowest humidity

It had gone 28 days without rain (1 mm or more) when it started. Rain came after the fire: 1.4 mm on 24 Jul.

This area had burned before

6% of the perimeter overlaps earlier fires recorded since 2016: 1,684 ha in 2016.

How big is it?

10 km
It burned the equivalent of 21% of the area of London (326 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

  1. Washoe where it started
    24,384 ha reached on 12 Jul
    1.4 %
  2. Lassen
    7,922 ha reached on 11 Jul
    0.6 %

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 2015
Built-up area0.68 ha
Residents≈ 30

Inside the perimeter there were about 0.68 hectares of built-up land and about 30 residents (GHSL 2015, 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 Rain Danger (FWI)
11 Jul 32.9 °C 9 % 46 km/h 0.0 mm Extreme 58
12 Jul 33.6 °C 10 % 44 km/h 0.0 mm Extreme 57
13 Jul 34.0 °C 12 % 46 km/h 0.0 mm Extreme 57
14 Jul 34.3 °C 12 % 36 km/h 0.0 mm Extreme 54
15 Jul 34.9 °C 7 % 40 km/h 0.0 mm Extreme 54
16 Jul 34.2 °C 7 % 52 km/h 0.0 mm Extreme 61
17 Jul 31.9 °C 11 % 57 km/h 0.0 mm Extreme 63
18 Jul after 31.2 °C 7 % 58 km/h 0.0 mm Extreme 62
19 Jul after 32.5 °C 7 % 49 km/h 0.0 mm Extreme 57
20 Jul after 31.5 °C 7 % 41 km/h 0.0 mm Extreme 56
21 Jul after 32.6 °C 9 % 26 km/h 0.0 mm Extreme 50
22 Jul after 34.7 °C 9 % 27 km/h 0.0 mm Very high 49
23 Jul after 34.7 °C 11 % 47 km/h 0.5 mm Extreme 57
24 Jul after 30.8 °C 16 % 38 km/h 1.4 mm High 34

Before and after, from space

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

Before · 4 Jul 2017
After · 24 Jul 2017

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 · 664Every 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 Long Valley Fire last?
The official perimeter only gives the start date (11 July 2017). The end comes from the heat detections inside the perimeter: it burned until 17 July 2017 (7 days from 11 July 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 32,578 hectares (325.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire entered 2 counties: Washoe (24,384 ha, 1.4 %); Lassen (7,922 ha, 0.6 %).
What was the weather like?
During the fire the temperature reached 34.9 °C, humidity dropped to 7 % and gusts hit 57 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

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.

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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. 664 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 2015, 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.