The massive blazes are sending plumes of smoke and ash into the skies surrounding San Francisco, fouling air quality for hundreds of miles and endangering public health. Evacuations expanded overnight Wednesday into the early morning hours Thursday, including portions of Travis Air Force Base, an Air Force logistics hub.
Late Wednesday, officials shut down Interstate 80 west of Vacaville, between San Francisco and Sacramento, as flames jumped the highway.
In central California, a pilot on a firefighting flight near Fresno died when his helicopter crashed, according to the Associated Press, and the National Transportation Safety Board is investigating.
Tens of thousands of people have been instructed to evacuate from advancing flames, with more told to be ready to flee if necessary.
The fires come as California has been enduring a record-breaking heat wave that has prompted rolling blackouts because of high electricity demands for air conditioning and other uses, as well as the coronavirus pandemic, which has killed more than 10,000 in the state.
In Solano County, southwest of Sacramento, officials ordered the evacuation of about 8,000 residents near the Russian River on Wednesday, and the SCU Lightning Complex in eastern San Francisco Bay is threatening nearly 3,800 homes and businesses in five counties.
According to the AP, one of the fires in Stanislaus County injured between five to seven people, including one who suffered major burns.
In San Mateo and Santa Cruz counties, southwest of San Francisco, about 20,000 people were ordered to evacuate because of a fire threatening communities there, part of the CZU Lightning Complex. Nearly two-dozen homes had burned as of Wednesday night, fire officials reported.
In a news conference Thursday morning, CalFire officials said the complex is unprecedented for that region in terms of its rapid growth and intensity.
“When you hear a term ‘sounds like a jet engine or a freight train,’ that’s exactly what it sounds like,” a Cal Fire chief said.
The state’s fire fighting resources are overextended, according to Gov. Gavin Newsom (D) and fire officials, given the number of large fires burning simultaneously. Cal Fire spokesman Jonathan Cox told the AP that some firefighters are working grueling 72-hour shifts instead of the typical 24-hour rotations.
“We’re in the unfortunate position where firefighters are going to be spending several days out on the fire line,” Cox said. “It’s grueling, it’s exhausting.”
Newsom originally appealed for aid from neighboring states, but expanded the state’s call for help to the entire country Wednesday as blazes raged out of control.
Concerns regarding the spread of covid-19 are limiting firefighting operations, wildfire expert Bill Stewart told the Sacramento Bee. “They can’t put as many firefighters next to each other on the fire line,” he said. “The pickup trucks (transporting crews) are historically full of people. Now they’re limited to one or two.”
The virus has also meant that prison firefighters are not being utilized due to coronavirus outbreaks in penitentiaries.
Here are key figures on the latest blazes:
- The LNU Lightning Complex in Sonoma, Lake, Napa and Solano counties has burned over 124,000 acres, up from 46,000 acres Wednesday, and is 0 percent contained. This complex includes the Hennessey Fire, which has charred 100,000 acres in Napa County.
- The CZU August Lightning Complex in Santa Cruz and San Mateo counties has burned 40,000 acres, up from 10,000 acres Wednesday, and is 0 percent contained. It has burned 20 structures and threatens 8,600 more. About 20,000 people have been evacuated.
- The SCU Lightning Complex of about 20 fires, affecting locations in Santa Clara, Alameda, Contra Costa, San Joaquin and Stanislaus counties, has consumed 102,000 acres, up from 85,000 acres Wednesday, and is 5 percent contained.
- The River Fire in Monterey County has consumed more than 15,000 acres, up from 10,000 acres Wednesday, and is 7 percent contained.
Elevated fire risk persists Thursday
Red flag warnings, signifying dangerous fire weather, remain in effect for large portions of northern California, away from coastal areas, in addition to other areas in the intermountain West.
The National Weather Service cautioned that locally gusty winds and a lack of increased overnight humidity levels means a continuation of “critical fire weather” through Thursday morning and, in some areas, the afternoon. Winds are forecast to gust to 20 to 30 mph in some vulnerable areas with relative humidity levels dropping below 40 percent and as low as 10 to 15 percent in some areas.
The National Weather Service in Sacramento wrote conditions are “warm and dry, though not as extreme as early Wednesday” in a forecast discussion.
After Thursday, the Sacramento forecast office calls for relative humidity to “trend up slightly” while temperatures cool some. Critical fire conditions are not forecast for California on Friday but conditions will remain dry in many areas allowing fires to linger.
Smoke will remain a persistent issue because of the ongoing fires, “so air quality will be a real problem through at least the end of the week,” the Sacramento office wrote.
Lightning plus an intense, late-season heat wave served as triggers
The fires stem from an unusual confluence of extreme weather events, set against the backdrop of human-caused global climate change, which is causing more frequent and severe heat waves in the region as well as larger wildfires across the West.
The immediate trigger of most of the more than two-dozen large fires burning in the Bay Area was an unusual August thunderstorm outbreak, which lit up the night skies above San Francisco on Sunday and Monday and moved inland, where lightning discharges struck trees and grasses at a time of year when vegetation is at its driest.
Between midnight Saturday and midnight Wednesday, there were 20,203 cloud-to-ground strikes in California, according to Chris Vagasky of Vaisala, which operates the National Lightning Detection Network. The total number of lightning discharges, which includes lightning that jumped from cloud to cloud without hitting the ground, was equivalent to 11 percent of California’s average annual lightning activity, he said via a message on Twitter.
The storms were the result of both moisture moving north from former Tropical Storm Fausto near the Baja Peninsula, and the sizzling heat across the state.
The long-lasting and intense heat wave has played a key role in these blazes. Multiple monthly heat records have been set in the past 10 days, including in Death Valley, Calif., where one of the hottest temperatures on Earth, a high of 130 degrees Sunday, was recorded.
One measure of fire risk is known as the evaporative demand drought index, or EDDI. It measures the “thirst” of the atmosphere and can help predict fire risk. In part because of the heat’s ability to speed up evaporation, the EDDI in central and northern California preceding these fires soared to record levels, indicating a high fire risk.