SAN FRANCISCO - Pacific Gas & Electric Co. began shutting off electricity Wednesday to 375,000 people in Northern and central California to prevent power lines from sparking wildfires as the region faced a new bout of windy and warm weather.
Some people in the wine country counties of Napa and Sonoma north of San Francisco lost power around 7 a.m. Power was also cut farther north in portions of Mendocino, Lake and Yolo counties, said Katie Allen, a PG&E spokeswoman.
Nearly 170,000 initially lost electricity, but the shut-offs that started Wednesday morning were expected to affect more people as the outages spread to 18 counties and last into Thursday.
A virtually rainless fall has left brush bone-dry and forecasts called for low humidity and winds gusting at times to 55 mph (89 kph), which might fling tree branches or other debris into power lines, causing sparks that could set catastrophic fires in the region, PG&E officials said.
The blackout is the latest in a series of massive outages by the country's largest utility, including one last month that affected nearly 2.5 million people and outraged local officials and customers who accused the utility of overkill. Officials have accused the company of using the blackouts as a crutch after years of failing to harden its infrastructure to withstand fire weather.
Corporation CEO Andy Vesey acknowledged the outages have been "terribly disruptive" and said the company is taking steps to avoid them in the future, but for now, "we won't roll the dice on public safety."
Meanwhile, California's utility regulators are demanding answers from wireless, internet and landline providers whose equipment failed during the previous outages, leaving hundreds of thousands of people without a way to get emergency alerts or make 911 calls.
Representatives from eight communications companies, including AT&T, Comcast/Xfinity, T-Mobile and Sprint, appeared Wednesday before the California Public Utilities Commission, fielding questions about whether they would support a rule requiring backup power and whether they would disclose outage information publicly and immediately during disaster situations.
Verizon, T-Mobile and AT&T officials said they would disclose outage information.
In a letter calling for the meeting, commission President Marybel Batjer said "lack of service is not a mere inconvenience - it endangers lives." She said residents do not have the luxury of failed internet or cellphone connections during a wildfire or other disaster.
Some local public officials who planned to speak at the hearing could not because of the latest power outage. And Lake County Supervisor Moke Simon made comments before rushing back to Northern California county, where the lights had gone out again.
He said AT&T's network went down right away during an outage in late October, risking the county's sewer and alarm systems. There was no backup in place, he said.
"That really put us in a dire straits situation," he said.
Batjer told communications company representatives she was surprised by their lack of preparation given California's long history of wildfires.
"It's sort of stunning that you go, 'Well, we just learned a lot in the last three weeks,'" she said.
More than 450,000 people were left without communications, according to a group representing rural counties in California. Half of Marin County's cell sites were out of service.
Consumer advocates urged the commission to establish backup power requirements and make the companies provide detailed information about outage locations.
The California Governor's Office of Emergency Services has called the companies' level of engagement unacceptable at a time when redundant infrastructure is necessary.
In written responses in advance of Wednesday's meetings, the companies said they did communicate with authorities but the outages were unprecedented in scope. The companies said they are improving backup power sources but added that doing so might not be possible in some locations and that generators are not always safe.
Comcast said that its network "like any modern network, fundamentally relies on commercial power to operate."
Meanwhile, warnings of extreme fire danger covered a large area. California's state fire agency placed fire engines and crews in position in some counties and had crews ready to staff aircraft and bulldozers.
The weather was expected to ease by Thursday morning, allowing PG&E to begin restoring power, said Mark Quinlan, PG&E's senior director of emergency preparedness and response.
One Napa County reporting station hasn't seen a measurable drop of rain since mid-September - the first time that's happened since 1905, said Scott Strenfel, PG&E's principal meteorologist.
The northern Sierra Nevada has seen a fraction of an inch of rain in the past two months instead of the usual 5 inches (13 centimeters), he said.
"This lack of rain is keeping the threat of fire very real, this late in the season, in many areas," Strenfel said.
In Southern California, wintry weather was bringing rain, wind and snow. A storm system dumped about 2 inches (6 centimeters) of rain in the San Diego County area on Tuesday and more was expected Wednesday.
Wet conditions made for a slippery Wednesday morning commute in Los Angeles while heavy flooding stranded drivers in desert areas to the east. Flash flood watches were in effect for some communities east of Los Angeles, with storm warnings up for mountain communities.
Voluntary evacuation warnings were issued for a few communities in an area of Orange and Riverside counties that was burned in a wildfire last year.