PHOTOS: Wildfire rages in Northern California

Flames consume a home as the Kincade Fire tears through the Jimtown community of Sonoma County, Calif., on Thursday, Oct. 24, 2019. (Photo: Noah Berger/AP)

SAN FRANCISCO (AP) — A Northern California wildfire exploded in size early Thursday as dangerously windy weather prompted the state's largest utility to impose electrical blackouts in an effort to prevent fire catastrophes.

The fire in the Sonoma County wine region north of San Francisco grew to more than 15 square miles (39 square kilometers) before dawn and authorities ordered evacuations near the small community of Geyserville.

There was no immediate information about what caused the fire, but wildfire risk was extremely high as humidity levels plunged and gusty winds up to 70 mph (113 kph) hit the region.

The Pacific Gas & Electric Co. utility on Wednesday began rolling blackouts stretching from the Sierra foothills in the northeast to portions of the San Francisco Bay Area in a bid to keep the electrical grid from causing fires due to wind that can send power lines toppling, starting fires.

Embers fly across a roadway as the Kincade Fire burns through the Jimtown community of Sonoma County, Calif., on Thursday, Oct. 24, 2019. (Photo: Noah Berger/AP)

The blackouts impacted a half-million people — or nearly 180,000 customers — in 15 counties, and PG&E warned that a second round of outages could occur over the weekend when winds return to the region.

Hot and dry Santa Ana winds were expected to hit Southern California Thursday and the Southern California Edison utility warned that it might black out about 308,000 customers — perhaps 750,000 people — depending on the forecast.

The San Diego Gas & Electric utility warned of power shutoffs to about 24,000 customers.

The utilities have said the precautionary blackouts are designed to keep winds that could gust to 60 mph (97 kph) or more from knocking branches into power lines or toppling them, sparking wildfires.

Firefighters confer while battling the Kincade Fire near Geyserville, Calif., on Thursday, Oct. 24, 2019. Portions of Northern California remain in the dark after Pacific Gas & Electric cut power to prevent wildfires from sparking during dry and windy conditions. (Photo: Noah Berger/AP)

Electrical equipment was blamed for setting several fires in recent years that killed scores of people and burned thousands of homes.

"We understand the hardship caused by these shutoffs," PG&E CEO Bill Johnson said Wednesday. "But we also understand the heartbreak and devastation caused by catastrophic wildfires."

The latest outage comes two weeks after PG&E shut down the power for several days to about 2 million people in northern and central California.

Read more of this story by the Associated Press on Yahoo News >>>

Flying embers from a destroyed fence are seen during the Kincade fire near Geyserville, California, U.S. October 24, 2019. (Photo: Stephen Lam/Reuters)
Two firefighters monitor the Kincade fire, near Geyserville, California, U.S. October 24, 2019. (Photo: Stephen Lam/Reuters)
Flames consume a home as the Kincade Fire tears through the Jimtown community of Sonoma County, Calif., on Thursday, Oct. 24, 2019. (Photo: Noah Berger/AP)
The Robert Young Estate Winery is seen as the Kincade fire burns in the distance, in Geyserville, California, U.S. October 24, 2019. (Photo: Stephen Lam/Reuters)
Embers fly from a tree as the Kincade Fire burns near Geyserville, Calif., on Thursday, Oct. 24, 2019. Portions of Northern California remain in the dark after Pacific Gas & Electric cut power to prevent wildfires from sparking during dry and windy conditions. (Photo: Noah Berger/AP)
Vines are silhouetted against the Kincade fire burning in a valley below, near Geyserville, California, U.S., October 24, 2019. (Photo: Stephen Lam/Reuters)
A car passes burning trees on Geysers Rd. as the Kincade Fire tears through unincorporated Sonoma County, Calif., on Thursday, Oct. 24, 2019. (Photo: Noah Berger/AP)
Cows stand on a ridge as the Kincade Fire approaches in unincorporated Sonoma County, Calif., on Thursday, Oct. 24, 2019. (Photo: Noah Berger/AP)

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