California, 2022

Wildfire in California, September 7 to 30, 2022

September 7 to 30, 2022 · NWS STO · 1 event in 1 county or zone

The Mosquito Fire began in Placer County 4 miles east of Foresthill near Mosquito Ridge Road, CA, and close to Oxbow Reservoir the evening of September 6, 2022, at 6:27 PM PDT and later spread into El Dorado County, CA. The cause is under investigation.

The toll

Deaths
0
Injuries
2
Property damage
None recorded
Crop damage
None recorded
Events
1

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS STO wrote it up.

The Mosquito Fire began in Placer County 4 miles east of Foresthill near Mosquito Ridge Road, CA, and close to Oxbow Reservoir the evening of September 6, 2022, at 6:27 PM PDT and later spread into El Dorado County, CA. The cause is under investigation. The fire started in extreme heat and very low humidity, in an area with drought conditions with exceptionally dry vegetation.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Sacramento, CA wrote its last area forecast discussion before the first event at Sep 7, 2:32 PM PST, 2 hours 55 minutes earlier.

Area forecast discussion, Sep 7, 2:32 PM PST, 2 hours 55 minutes before
Area Forecast Discussion
National Weather Service Sacramento CA
332 PM PDT Wed Sep 7 2022

.Synopsis...
Dangerous heat will persist through the end of the week. Monsoon
moisture will bring a slight chance of thunderstorms to the
northern Sierra Nevada. A more significant moisture surge is
possible over the weekend.

&&

.Discussion...

Main story continues to be the significant heatwave. While the
hottest part of the current extended heatwave occurred yesterday,
the impacts will continue to be felt through the end of the week
as the successive hot days and warm nights add up resulting in
continuing very high heat risk. Highs today have not been as
extreme as Tuesday's as the ridge is temporarily flattened by a
trough moving through the PacNW and induced onshore flow, but
widespread daily records will likely be challenged.

Temperatures bump up a few degrees again on Thursday as the ridge
rebounds and northerly surface flow returns. Temperatures are
expected to start edging down Friday (but still very hot), and
further on Saturday (still quite hot) as the ridge breaks down.

Some mid-level moisture rotating around the periphery of the high
pressure system will continue to keep isolated shower and
thunderstorm chances in the forecast for the Sierra-Nevada through
the rest of the week. Additionally, with continued presence of
mid- level moisture coupled with enhanced lift from a low
pressure system moving through the PacNW today, some showers and
a few thunderstorms have developed across northern CA. These
showers are expected to mainly remain outside of the northern
Sacramento Valley, and continue to move across northwestern
Shasta County through this afternoon. Given dry low- levels, any
stronger showers/storms may produce locally gusty winds and a
stray dry lightning strike may be possible.

&&
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...

Long wave trough approaches the West Coast Sunday into early next
week as embedded short waves move through PacNW. Lingering
moisture from Hurricane Kay over the area will result in increased
cloudiness and cooler temperatures. Below normal high temperatures
expected with cooling trend Sunday into Wednesday. Threat of
showers or thunderstorms possible each day over portions of the
eastern foothills and mountains.

&&

.AVIATION...

VFR conditions expected over the next 24 hours. Isolated -SHRA/-TSRA
over mountain crests thru 04Z. Surface wind generally below 12 knots
with local gusts up to 20 knots over the Delta.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM PDT Friday for Carquinez
Strait and Delta-Central Sacramento Valley-Motherlode-Mountains
Southwestern Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Shasta Lake Area / Northern Shasta County-
Southern Sacramento Valley-West Slope Northern Sierra Nevada-
Western Plumas County/Lassen Park.

&&

Event by event

1 wildfire. Local standard time, as filed.

Wildfire, West Slope Northern Sierra Nevada

When
September 7, 5:27 PM PST to September 30, 11:59 PM PST
Where
West Slope Northern Sierra Nevada forecast zone
Injuries
2 direct, 0 indirect
Reported by
Fire Department/Rescue

The Mosquito Fire started on September 6th, which had all-time record high temperatures in the area set and extremely low humidity dropping into the single digits. Extreme fire behavior was observed due to the very dry humidity and fuels, with the fire developing large plumes that radar indicated extended up to 40,000 feet. In the first few days, the fire saw rapid growth at 5,705 acres by 7 pm PDT on the 7th and 13,705 acres by 8 pm PDT on the 8th. More than 11,000 people were evacuated and 9,000 structures were threatened. The fire included areas in both the Tahoe and Eldorado National Forests. The fire burned a total of 76,788 acres and caused road closures throughout the area. There were 2 firefighters injured during the fire. A total of 78 structures were destroyed and an additional 13 buildings were damaged in the towns of Foresthill, Volcanoville, and Michigan Bar. Periods of moderate to heavy rain from September 18-21 largely halted fire growth, but the fire was not considered fully contained until October 22.

What these are

Wildfire
A fire burning in wildland vegetation, with its acreage and damage where known.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in California in 2022Every state in 2022This day in weather historyWarnings in California, September 2022

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1058215.