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Big Grassy Fire, July 2018 Malheur

Out · last measured on 24 Jul 2018

The fire started on 24 July 2018 in Malheur, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 2,127 hectares, spread across a single county.

It is the 163th largest in Oregon since 2016 (of 327 with a page). Number 190 in United States in 2018, of 511.

Compare with…

Suggestions: Drummond Basin · 2019Bowden · 2017Bowden · 2024Butte · 2025

We have the official perimeter (MTBS / NIFC) for this fire, but the VIIRS sensors did not capture it in enough detail: no day-by-day evolution, but the split by county is there.

Burnt area
2,127ha
official perimeter (MTBS / NIFC)
Duration
1day
24 Jul 2018 – 24 Jul 2018
Counties hit
1
counties
Started on
24 Jul
2018
Danger at start
55
Extreme · FWI index

Where it burned

The weather it burned in

36°high
36km/h · peak gust
13%lowest humidity

It had gone 35 days 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.

How big is it?

10 km
It burned the equivalent of 1.3% of the area of London (21 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. Malheur where it started
    2,098 ha
    0.1 %

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 area< 0.1 ha
Residents< 20

Inside the perimeter there was no noticeable built-up land and almost nobody lived there (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 Rain Danger (FWI)
24 Jul 36.5 °C 13 % 36 km/h 0.8 mm Extreme 55
25 Jul after 35.4 °C 12 % 32 km/h 0.0 mm Extreme 57
26 Jul after 35.2 °C 10 % 34 km/h 0.0 mm Extreme 62
27 Jul after 35.1 °C 9 % 35 km/h 0.0 mm Extreme 60
28 Jul after 33.9 °C 6 % 34 km/h 0.0 mm Extreme 62
29 Jul after 34.4 °C 9 % 31 km/h 0.0 mm Extreme 58
30 Jul after 35.8 °C 6 % 29 km/h 0.0 mm Extreme 60
31 Jul after 33.8 °C 12 % 40 km/h 0.2 mm Extreme 70
1 Aug after 34.9 °C 9 % 38 km/h 0.0 mm Extreme 65
2 Aug after 33.1 °C 7 % 36 km/h 0.0 mm Extreme 62
3 Aug after 29.6 °C 9 % 41 km/h 0.0 mm Extreme 64

Before and after, from space

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

Before · 17 Jul 2018
After · 31 Jul 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.

Other fires nearby

All fires in United States ›

Frequently asked questions

How long did the Big Grassy Fire last?
It burned between 24 July 2018 and 24 July 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 2,127 hectares (21.3 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?
The fire only entered Malheur (2,098 ha, 0.1 %).
What was the weather like?
During the fire the temperature reached 36.5 °C, humidity dropped to 13 % and gusts hit 36 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

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.
  • Dates from the perimeter: the VIIRS detections inside it did not change them. No 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.