SAN FRANCISCO – A California utility cut power to 12 northern counties as a major “diablo wind” – known in fall for its hot, dry gusts – increased the risk of power lines sparking a fire of forest.

About 13,000 customers woke up without power Friday after Pacific Gas and Electric cut power.

The “diablo wind” is expected to bring sustained winds reaching 35 mph (56 kph) in many areas, with possible gusts exceeding 65 mph (104 kph) along mountain peaks, according to the National Weather Service. Strong winds are expected to persist through part of the weekend.

The utility began cutting power Thursday evening to customers in 12 counties, including Alameda, Contra Costa, Napa, Solano and Sonoma in the Bay Area, and to some customers farther north in Colusa, Glenn, Tehama counties and Shasta, PG&E said.

In total, about 20,000 customers could be temporarily without power in the coming days, PG&E said in a statement Thursday.

Forecasters issued fire danger warnings through Saturday from the Central Coast to the San Francisco Bay area and into northern Shasta County, not far from the Oregon border.

“This could become the most significant wind event of this year so far,” said meteorologist Brayden Murdock of the service’s Bay Area office. “We want to tell people to be careful.”

During a diablo wind, common in the fall, the air is so dry that relative humidity levels drop, drying out vegetation and preparing it to burn. The name – “diablo” means “devil” in Spanish – is informally applied to a warm wind that blows near the San Francisco area from the interior toward the coast as high pressure develops over the west.

Targeted power outages were also possible in Southern California, where another notorious weather phenomenon, Santa Ana winds, is expected Friday and Saturday.

The Santa Anas are dry, warm, gusty northeast winds that blow from southern California’s interior toward the coast and offshore, moving in the opposite direction to the normal land flow that carries moist air from the Pacific to the region.

The National Weather Service has issued red flag warnings for the valleys and mountains of Los Angeles County, parts of the Inland Empire and the San Bernardino Mountains.

Winds around greater Los Angeles won’t be as strong as in the north, with gusts between 25 and 40 mph possible in the mountains and foothills, said Mike Wofford, a meteorologist with the Weather Service’s Los Angeles regional office. Angeles.

“I think it will be more moderate,” he said Wednesday. “But the risk of fire is still present.”

But snow is forecast for mountain peaks around Lake Tahoe, where up to 2 inches were forecast Friday morning, according to the National Weather Service in Reno, Nevada. Winds around Lake Tahoe could reach 70 mph (113 km/h).

The service also issued its first frost warning of the season along the Eastern Sierra Front, in effect from 2 a.m. to 9 a.m. Friday, from south of Carson City north through Reno to the Lassen, Sierra and Plumas counties in California, where temperatures could dip into the low temperatures. 20s Fahrenheit (-5 Celsius).

“Freezing and freezing conditions could kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing,” the service said.