How long did the Helena fire last?

It burned between 31 August 2017 and 31 August 2017: 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 7,566 hectares (75.7 km²). Other tallies, such as daily incident reports, may give slightly different figures.

Which counties burned?

The fire only entered Trinity (7,588 ha, 0.9 %).

What was the weather like?

During the fire the temperature reached 39.1 °C, humidity dropped to 7 % and gusts hit 53 km/h. The fire danger index (FWI) reached 51, 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 · 2017-08-31 → 2017-08-31

Helena Fire, August 2017 Trinity

Out · last detection 1 Sept 2017, 21:49 UTC

The fire started on 31 August 2017 in Trinity, United States, and satellites saw it burning for 1 day. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 7,566 hectares, spread across a single county.

It is the 103th largest in California since 2016 (of 442 with a page). Number 101 in United States in 2017, of 619.

Burnt area: 7,566ha; official perimeter (MTBS / NIFC)
Duration: 1day; 31 Aug 2017 – 31 Aug 2017
Municipalities hit: 1; counties
Started on: 31 Aug; 2017
Heat detections: 963; in a single hotspot: 151 MW
Danger at start: 45; Very high · FWI index
Energy released: 1.2GW; sum of detected power

Play back 1 Sept 2017

HOTSPOTS BY DAY 31 Aug31 Aug

How it evolved, day by day

311

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

The weather it burned in

39°high

53km/h · peak gust

7%lowest humidity

It had gone 8 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.

What happened to each town

Trinity where it started

7,588 ha reached on 31 Aug

0.9 %

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)
31 Aug	35.2 °C	11 %	31 km/h	0.0 mm	Very high 45
1 Sept after	39.0 °C	7 %	29 km/h	0.0 mm	Very high 50
2 Sept after	39.1 °C	9 %	30 km/h	0.0 mm	Very high 49
3 Sept after	37.1 °C	13 %	26 km/h	0.0 mm	Very high 49
4 Sept after	36.1 °C	13 %	37 km/h	0.0 mm	Extreme 51
5 Sept after	35.1 °C	22 %	34 km/h	0.2 mm	Very high 46
6 Sept after	30.3 °C	35 %	42 km/h	0.9 mm	High 27
7 Sept after	22.0 °C	61 %	53 km/h	2.1 mm	Low 7
8 Sept after	27.8 °C	33 %	28 km/h	2.2 mm	Low 8
9 Sept after	29.9 °C	28 %	30 km/h	0.0 mm	High 23
10 Sept after	33.9 °C	18 %	20 km/h	0.0 mm	High 32
11 Sept after	34.8 °C	17 %	35 km/h	0.0 mm	Very high 39
12 Sept after	30.8 °C	27 %	22 km/h	0.5 mm	High 34
13 Sept after	31.1 °C	20 %	40 km/h	0.0 mm	High 35
14 Sept after	23.1 °C	22 %	53 km/h	0.0 mm	High 38
15 Sept after	25.4 °C	15 %	28 km/h	0.0 mm	High 33
16 Sept after	25.6 °C	18 %	27 km/h	0.0 mm	High 32
17 Sept after	25.3 °C	20 %	44 km/h	0.0 mm	Very high 39
18 Sept after	17.7 °C	41 %	53 km/h	0.8 mm	High 22
19 Sept after	15.9 °C	48 %	45 km/h	0.0 mm	Moderate 20
20 Sept after	15.9 °C	47 %	50 km/h	1.1 mm	Moderate 13
21 Sept after	15.9 °C	29 %	40 km/h	0.1 mm	Moderate 19
22 Sept after	18.7 °C	23 %	18 km/h	0.0 mm	Moderate 21
23 Sept after	22.3 °C	20 %	26 km/h	0.0 mm	High 26
24 Sept after	24.6 °C	18 %	25 km/h	0.0 mm	High 29
25 Sept after	27.2 °C	18 %	33 km/h	0.0 mm	High 32
26 Sept after	28.3 °C	18 %	43 km/h	0.0 mm	High 37
27 Sept after	28.9 °C	10 %	30 km/h	0.0 mm	Very high 40
28 Sept after	28.6 °C	14 %	30 km/h	0.0 mm	Very high 39
29 Sept after	23.8 °C	32 %	35 km/h	0.2 mm	High 31
30 Sept after	23.3 °C	20 %	47 km/h	0.0 mm	High 35
1 Oct after	20.4 °C	18 %	47 km/h	0.0 mm	High 35
2 Oct after	18.3 °C	18 %	42 km/h	0.0 mm	High 35
3 Oct after	21.0 °C	12 %	49 km/h	0.0 mm	Very high 39
4 Oct after	22.4 °C	12 %	32 km/h	0.0 mm	High 35
5 Oct after	24.2 °C	9 %	17 km/h	0.0 mm	High 36
6 Oct after	30.0 °C	5 %	31 km/h	0.0 mm	Very high 46
7 Oct after	25.2 °C	18 %	47 km/h	0.0 mm	Very high 44

Before and after, from space

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

↔

Before · 24 Aug 2017

After · 7 Sept 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 · 963Every 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 Helena fire last?: It burned between 31 August 2017 and 31 August 2017: 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 7,566 hectares (75.7 km²). Other tallies, such as daily incident reports, may give slightly different figures.
Which counties burned?: The fire only entered Trinity (7,588 ha, 0.9 %).
What was the weather like?: During the fire the temperature reached 39.1 °C, humidity dropped to 7 % and gusts hit 53 km/h. The fire danger index (FWI) reached 51, 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

Satellite cross-check

NASA FIRMS ↗
NIFC · Fire maps ↗

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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