SAN FRANCISCO (AP) — A California utility has shut off power in 12 counties in the northern part of the state as a strong “Diablo wind” — notorious for its hot, dry gusts in the fall — has increased the risk of downing power lines could cause a wildfire.

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

According to the National Weather Service, the “Diablo wind” is expected to produce sustained winds of 35 mph (56 km/h) in many areas, with possible gusts of over 60 mph (100 km/h) on mountain peaks. Strong winds are expected to continue for part of the weekend.

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

In total, about 20,000 customers could temporarily lose power over the next few days, PG&E said in a statement Thursday.

READ MORE: The Diablo and Santa Ana winds could sweep across California, increasing the risk of wildfires

Meteorologists issued fire warnings through Saturday from the central coast through the San Francisco Bay Area to northern Shasta County, not far from the Oregon border.

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

During a Diablo wind, which is common in the fall, the air is so dry that relative humidity drops, vegetation dries out and is ready to burn. The name – “Diablo” is Spanish for “devil” – is used informally for a hot wind that blows inland toward the coast near the San Francisco region as high pressure builds to the west.

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

Santa Anas are dry, warm, gusty northeasterly winds that blow toward and offshore from the interior of Southern California, moving in the opposite direction of the normal overland flow that carries moist air from the Pacific into the region.

READ MORE: “Hellish” trio of wildfires endanger communities in Southern California

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

Winds in the greater Los Angeles area will not be as strong as in the north, with gusts between 25 and 40 miles per hour (40 and 64 km/h) possible in mountains and foothills, said Mike Wofford, a meteorologist in the weather service's office in the area Los Angeles.

The strongest winds were recorded in the Santa Monica and San Gabriel mountains, where there were gusts between 45 and 55 mph Friday and isolated gusts of up to 60 mph, he said.

“The humidity is drying out and we have winds. If we had a spark of fire, it could spread very quickly given the current conditions,” Wofford said.

According to the National Weather Service in Reno, Nevada, some mountain peaks around Lake Tahoe received light snow overnight Friday. Temperatures near freezing point are expected again from Friday evening to Saturday

Wind sensors on two peaks west of Lake Tahoe recorded wind speeds of 75 and 104 miles per hour Friday. Strong winds are expected to continue through the night before easing Saturday morning, the National Weather Service said.

The service also issued its first freeze warning of the season along the eastern Sierra front, effective 2 a.m. to 9 a.m. Friday, from south of Carson City north through Reno into Lassen, Sierra and Plumas counties in California, where temperatures will drop to lows could be 20s Fahrenheit.

“Frost and freeze conditions could kill crops and other sensitive vegetation and potentially damage unprotected outdoor plumbing,” the service said.