Updated Sep 15, 2022 - Science

Swelling Mosquito Fire now California's largest wildfire this year

 CalFire Placer Crew firefighters monitor a backfire during the Mosquito fire in Foresthill, an unincorporated area of Placer County, California on September 13.

Cal Fire Placer Crew firefighters monitor a backfire during the Mosquito fire in Foresthill, an unincorporated area of Placer County, California, on Tuesday. Photo: Josh Edelson/AFP via Getty Images

Northern California's Mosquito Fire in the Sierra Nevada foothills swelled to 63,776 acres on Wednesday evening after "critically dry fuels" drove rapid growth, per Cal Fire.

Threat level: Evacuation orders and warnings remained in place for affected communities northeast of Sacramento as the blaze burned across El Dorado and Placer counties at 20% containment and became the largest recorded in California this year.

  • As poor air quality looms, schools in the area halted in-person classes, including in the Washoe County School District, The University of Nevada, Reno and Truckee Meadows Community College, AP reports.

State of play: Lighter southwesterly winds than Tuesday helped clear some of the air in fire-affected areas and firefighters were holding the Mosquito Fire inside control lines with the help of cooler temperatures and higher humidity, according to Cal Fire's incident report.

Yes, but: "The fire remains active on this eastern front, steadily burning and advancing in heavy unburned fuels," Cal Fire said.

  • The priority was "strengthening and securing the southwest corner" of the fire that ignited Sept. 6 "to protect and defend the communities of Foresthill and Todd Valley."

What they're saying: Cal Fire fire behavior analyst Jonathan Pangburn said during a briefing earlier this week that authorities had expected an increase in fire behavior in the area due to "historically dry fuels."

  • Pangburn compared the dry fuel conditions firefighters were facing in tackling the Mosquito Fire to the King Fire, east of Sacramento, which burned more than 97,000 acres in 2014 — when they deployed emergency fire shelters in some areas due to the rapidly moving blaze.
  • "Those events were similar to this, not wind-driven events, just fuel that was primed and ready and decided to get up with a hurry and put some people in some dangerous situations," Pangburn said, per the Los Angeles Times.
  • "We're ready for an absolute blowup out here."

The big picture: California Gov. Gavin Newsom last week declared a state of emergency for counties threatened by the Mosquito and Fairview Fires.

  • The Fairview Fire, near Hemet, which killed two people earlier this month, has destroyed more than 28,300 acres in Riverside County and was 75% contained as of Wednesday, according to Cal Fire.

By the numbers: 91 large fires were burning on Wednesday across eight states in the Western U.S. — including 10 in California, according to the latest information from the National Interagency Fire Center.

  • The McKinney Fire, near the border with Oregon, which was previously the largest wildfire to burn in California this year, has razed 60,138 acres and was 99% contained on Wednesday, according to Inciweb.

Context: Most of the U.S. West is experiencing drought conditions — particularly the Southwest, where an ongoing megadrought is the most severe such event in at least 1,200 years, per Axios' Andrew Freedman.

Go deeeper: One extreme climate event can worsen others, studies show

Editor's note: This article has been updated with new details throughout.

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