Elijah Carter 11, left, and Robert Haralson, 12, help shop for their parents Wednesday in a darkened Olivers Supermarket in the Rincon Valley community in Santa Rosa, Calif. The west side of the store was lit by patio lights powered by a generator as power was shut off again by Pacific Gas & Electric Co. due to high fire danger. (Kent Porter/The Press Democrat via AP)

SAN FRANCISCO (AP) — Dangerously windy weather sweeping through the state brought power outages to Northern California as the state’s largest utility staged blackouts designed to prevent catastrophic wildfires.

Pacific Gas & Electric Co. on Wednesday began rolling blackouts stretching from the Sierra foothills in the northeast to portions of the San Francisco Bay Area. A couple of counties kept their power until after midnight.

The blackouts impact 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.

Meanwhile, a wind-driven wildfire has forced evacuations north of San Francisco in Sonoma County. The blaze near Geyserville had grown to 10,000 acres (15 square miles) by early today, according to the state firefighting agency Cal Fire. Winds around the county’s highest areas were blowing at speeds up to 70 mph, and elsewhere in the region between 30 mph and 50 mph, the National Weather Service said.

In the south, where hot, dry Santa Ana winds were expected to hit today, Southern California Edison warned that it might black out about 308,000 customers — perhaps 750,000 people — depending on the forecast.

San Diego Gas & Electric 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 or more from knocking branches into power lines or toppling them, sparking wildfires.

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.

The current outages will last about 48 hours, the utility said. But its seven-day forecast shows a likelihood of another planned blackout across a much larger area. The timing wasn’t clear but it could start as early as Saturday, when even heavier winds are expected to move through.

“This could be the strongest wind event of the season, unfortunately,” PG&E meteorologist Scott Strenfel said.

Strenfel called the current wind event a “California-wide phenomenon.”

The small city of Calistoga, in the Napa Valley, known for its hot springs and wineries, was among those hit by Wednesday’s outage.

“It’s very frustrating,” said Michael Dunsford, owner of the 18-room Calistoga Inn, which has rented two powerful generators for the month at a cost of $5,000. Like many, he felt the outages need to be better managed, better targeted and less expansive.

“Right now, we have no wind. Zero. I don’t even see a single leaf blowing. Did they really have to cut the power right now?” he said, shortly after the lights went out Wednesday afternoon and he revved up the generators. “When the wind picks up to 40 mph maybe that’s a good time to close the power.”

“They’re not appreciating enough the impact this has on everybody,” he said about PG&E.