SAN FRANCISCO — Pacific Gas & Electric began shutting off power to about 25,000 customers in central and northern California Monday and Southern California Edison warned it may do the same for up to 9,000 of its customers as high winds toppled trees, downed power lines and ignited fires that forced people to flee from their homes.

At least a half dozen mostly small fires broke out across the state, challenging firefighters as they tried to contain the blazes amid the blustering wind.

West of Santa Barbara, authorities ordered the mandatory evacuation of campsites, cattle and horse ranches near Refugio State Beach and shut U.S. 101 — the only highway along the coast — as winds pushed a fire that started in the Los Padres National Forest toward the beach, U.S. Forest Service spokesman Andrew Madsen said.

The fire was driven through dense chaparral by winds gusting to 70 mph. It had grown to at least 4.5 square miles by nightfall and threatened perhaps 100 homes, ranches and other buildings, authorities said.

About 200 firefighters were battling the flames and trying to protect homes and buildings but aircraft couldn’t help because they were grounded by the high winds, fire officials said.

Firefighters in Fresno Rescue 3 From Home After Fallen Treen

In the San Joaquin Valley, a grass fire north of Madera prompted evacuations east of State Route 99. Meanwhile, firefighters in Fresno rescued three people trapped in their home after a tree fell on it.

California already has seen massive fires this year, including one that may have burned hundreds of giant sequoias in groves in Sequoia National Park in the Sierra Nevada. On Monday, a firefighter with a hand crew working on the blaze was struck by a falling rock. The firefighter was airlifted to a hospital and is in stable condition, fire officials said.

Forecasters issued a red flag warning for extreme fire danger from gusty winds. The warning extends until late Tuesday. The strongest winds are expected most of Monday, said Hannah Chandler-Cooley, a meteorologist with the National Weather Service in Sacramento.

The planned outages are necessary because high winds, combined with low humidity and drought-ravaged vegetation, could raise the risk of trees falling on power lines and spark a fast-spreading wildfire, PG&E said in a statement. Heat waves and historic drought tied to climate change have made wildfires harder to fight in California and the rest of the U.S. West.

Toppled Trees Spark Fires, Damaging Homes

On the Central Coast, a tree fell onto power lines at Hearst San Simeon State Park, sparking a small fire in the brush, the California Department of Forestry and Fire Protection tweeted.

Winds were expected to pick up Monday afternoon to evening in Southern California, with projected gusts of 50 to 70 mph. SoCal Edison began turning off power to a customers in parts of Los Angele and Ventura counties to reduce the threat of wildfires.

The National Weather Service said blowing dust was widespread from the Sacramento Valley, across the San Joaquin Valley and into the high desert Antelope Valley north of Los Angeles. Caltrans said sections of State Route 138 near the Antelope Valley city of Lancaster and State Route 14 were shut down because of the dust storm and several overturned trucks blocking the roadway.

Strong winds knocked down a tree, destroying three parked cars and damaging a home in the coastal town of El Granada, in San Mateo County, CalFire said.

No one was injured, but photos from the scene showed the tree also took down power lines.

PG&E Says Power Expected Tuesday

PG&E said it expects to begin restoring power Tuesday afternoon.

The utility began intentionally shutting off power in the fall of 2019 to prevent wildfires, after an investigation determined the Camp Fire that wiped out most of the town of Paradise was sparked by its equipment. The company filed for bankruptcy and pleaded guilty to 84 counts of involuntary manslaughter related to the 2018 fire.

PG&E also faces numerous criminal charges for fires caused by its fraying equipment, including involuntary manslaughter charges filed last month in connection to a wildfire near the city of Redding last year that killed four people.