Hennessey Fire, August 2020 Napa, Yolo, Solano
The fire started on 17 August 2020 in Napa, United States, and satellites saw it burning for 16 days. United States agencies (MTBS / NIFC) mapped an official burnt perimeter of 127,077 hectares, spread across 5 counties.
It is the 8th largest in California since 2016 (of 442 with a page). Number 5 in United States in 2020, of 441.
Compare with…
Suggestions: County · 2018Atlas · 2017Cold · 2016Winter · 2017
- Burnt area
- 127,077ha
- official perimeter (MTBS / NIFC)
- Duration
- ≈ 16days
- 17 Aug 2020 – 1 Sept 2020
- Counties hit
- 5
- counties
- Started on
- 17 Aug
- 2020
- Heat detections
- 7,306
- in a single hotspot: 868 MW
- Danger at start
- 46
- Very high · FWI index
- Average daily power
- 13.8GW
- detected power per day, on average
Where it burned
How it evolved, day by day
Fire radiative power detected each day, in megawatts, and number of hotspots. The magenta bar marks the peak day.
The weather it burned in
It had gone more than two months without rain (1 mm or more) when it started.
This area had burned before
27% of the perimeter overlaps earlier fires recorded since 2016: 2,454 ha in 2016, 5,423 ha in 2017, 28,704 ha in 2018, 428 ha in 2019. Part of it burned more than once, so the yearly figures add up to more than the 34,195 ha that had burned before.
- 28,108 ha County fire, June 2018 37,390 ha in total; the hectares shown are those it shares with this fire
- 4,430 ha Atlas fire, October 2017 20,894 ha in total; the hectares shown are those it shares with this fire
- 2,454 ha Cold fire, August 2016 2,544 ha in total; the hectares shown are those it shares with this fire
- 993 ha Winter fire, July 2017 1,004 ha in total; the hectares shown are those it shares with this fire
- 428 ha Sand fire, June 2019 1,000 ha in total; the hectares shown are those it shares with this fire
- 304 ha Nelson fire, August 2018 892 ha in total; the hectares shown are those it shares with this fire
- 292 ha Snell fire, September 2018 1,009 ha in total; the hectares shown are those it shares with this fire
How big is it?
London boundary: geoBoundaries · Office for National Statistics (Open Government Licence v3.0).
Paris boundary: geoBoundaries · Institut national de l'information géographique et forestière (IGN-F) (Etalab Open License 2.0).
Madrid boundary: geoBoundaries · Open Data ESRI, IGN Central Registry of Cartography Area (CC BY 4.0).
Berlin boundary: geoBoundaries · Federal Agency for Cartography and Geodesy (dl-de/by-2-0).
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 started68,459 ha reached on 18 Aug33 %
-
31,544 ha reached on 19 Aug12 %
-
16,690 ha reached on 18 Aug7.2 %
-
10,134 ha reached on 19 Aug2.9 %
-
595 ha reached on 27 Aug0.2 %
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 2020Inside the perimeter there were about 165 hectares of built-up land and about 3,600 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 | Rain | Danger (FWI) |
|---|---|---|---|---|---|
| 17 Aug | 39.8 °C | 19 % | 35 km/h | 0.6 mm | Very high 46 |
| 18 Aug | 42.8 °C | 8 % | 47 km/h | 0.0 mm | Extreme 61 |
| 19 Aug | 40.0 °C | 8 % | 45 km/h | 0.0 mm | Extreme 62 |
| 20 Aug | 38.4 °C | 8 % | 30 km/h | 0.0 mm | Extreme 55 |
| 21 Aug | 37.5 °C | 21 % | 34 km/h | 0.0 mm | Very high 49 |
| 22 Aug | 37.6 °C | 20 % | 35 km/h | 0.0 mm | Very high 49 |
| 23 Aug | 37.1 °C | 13 % | 32 km/h | 0.2 mm | Extreme 51 |
| 24 Aug | 35.9 °C | 18 % | 37 km/h | 0.0 mm | Very high 48 |
| 25 Aug | 34.8 °C | 26 % | 35 km/h | 0.0 mm | Very high 44 |
| 26 Aug | 34.0 °C | 26 % | 37 km/h | 0.0 mm | Very high 43 |
| 27 Aug | 34.6 °C | 19 % | 24 km/h | 0.0 mm | High 37 |
| 28 Aug | 35.8 °C | 18 % | 32 km/h | 0.0 mm | Very high 43 |
| 29 Aug | 34.9 °C | 25 % | 37 km/h | 0.0 mm | Very high 44 |
| 30 Aug | 35.6 °C | 20 % | 30 km/h | 0.0 mm | Very high 41 |
| 31 Aug | 36.3 °C | 18 % | 33 km/h | 0.0 mm | Very high 41 |
| 1 Sept | 37.0 °C | 19 % | 36 km/h | 0.0 mm | Very high 43 |
| 2 Sept after | 34.1 °C | 28 % | 29 km/h | 0.0 mm | Very high 38 |
| 3 Sept after | 36.4 °C | 25 % | 35 km/h | 0.0 mm | Very high 41 |
| 4 Sept after | 39.5 °C | 14 % | 32 km/h | 0.0 mm | Very high 48 |
| 5 Sept after | 42.4 °C | 8 % | 22 km/h | 0.0 mm | Extreme 51 |
| 6 Sept after | 45.6 °C | 6 % | 26 km/h | 0.0 mm | Extreme 57 |
| 7 Sept after | 45.9 °C | 5 % | 40 km/h | 0.0 mm | Extreme 59 |
| 8 Sept after | 33.7 °C | 6 % | 68 km/h | 0.0 mm | Very extreme 83 |
| 9 Sept after | 31.7 °C | 8 % | 41 km/h | 0.0 mm | Extreme 61 |
| 10 Sept after | 28.5 °C | 22 % | 32 km/h | 0.0 mm | Very high 43 |
| 11 Sept after | 33.3 °C | 20 % | 24 km/h | 0.0 mm | Very high 40 |
Before and after, from space
Drag the line to compare the same ground before the fire and after it.
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 · 7,306Every satellite heat detection, one by one, with time, satellite, power and coordinates.
| Date and time | Satellite | FRP (MW) | Lat | Lon |
|---|
Other fires nearby
- 37,390 haCounty YoloJune 2018 · 19 days · 9 km away
- 2,544 haCold YoloAugust 2016 · 3 days · 19 km away
- 2,760 haPickett NapaAugust 2025 · 5 days · 21 km away
- 27,507 haGlass NapaSeptember 2020 · 27 days · 26 km away
- 20,894 haAtlas NapaOctober 2017 · 7 days · 29 km away
- 23,002 haNuns SonomaOctober 2017 · 10 days · 36 km away
Frequently asked questions
- How long did the Hennessey Fire last?
- The official perimeter only gives the start date (17 August 2020). The end comes from the heat detections inside the perimeter: it burned until 1 September 2020 (16 days from 17 August 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 127,077 hectares (1,270.8 km²). Other tallies, such as daily incident reports, may give slightly different figures.
- Which counties burned?
- The fire entered 5 counties: Napa (68,459 ha, 33 %); Yolo (31,544 ha, 12 %); Solano (16,690 ha, 7.2 %); Lake (10,134 ha, 2.9 %); Colusa (595 ha, 0.2 %).
- What was the weather like?
- During the fire the temperature reached 42.8 °C, humidity dropped to 8 % and gusts hit 47 km/h. The fire danger index (FWI) reached 62, 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 ›
- NIFC · National Interagency Fire Center ↗
- InciWeb · Incident Information System ↗
- MTBS · Monitoring Trends in Burn Severity ↗
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.
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
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. 7,306 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.
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.