LOS ANGELES — Hundreds of thousands of residents of Northern California whose power will be shut off in the next two days got even worse news Wednesday: Another, even larger, blackout is likely over the weekend.

The state's largest utility, Pacific Gas and Electric Corp., or PG&E, began shutting off electricity to nearly a half-million people Wednesday afternoon, the second massive blackout in two weeks. It said hot, dry winds and low humidity were creating a high risk of sparks and "rapid wildfire spread" from its long-neglected power lines.

The blackouts will eventually spread to parts of 17 counties — including such large communities as Santa Rosa, Sonoma and Napa but not San Francisco or San Jose — at least through Thursday afternoon and through Friday afternoon in other parts of the region, PG&E said.

Mark Quinlan, PG&E's director of environmental health and safety, said that's when the last of the dangerous conditions are expected to end, and only then can its crews go out to inspect 8,000 miles of power lines for damage.

A brush fire that broke out Wednesday night in rural Sonoma County had grown to thousands of acres by early Thursday, leading to evacuation orders for about 2,000 people.

In the southern part of the state, Southern California Edison began cutting off power to almost 27,000 customers on Thursday and said it was considering shutoffs to almost 400,000 more. The potential coverage area includes such large communities as San Bernardino, Malibu, Irvine, Glendale and Palm Springs but not Los Angeles itself, which is served by a separate power company.

A power "customer" can be a single residence or a large business; a standard conversion that many utilities use assesses 2½ people per customer, meaning as many as 450,000 people could be affected in Northern California. Southern California Edison's potential blackouts could affect more than 1 million.

At the famed Alice's Restaurant in Woodside, in San Mateo County, owner Jamie Kerr bemoaned the "major frustration."

"I think that's the sentiment you're getting across the board," Kerr told NBC Bay Area.

Loran Cary of Woodside said he thought PG&E was "going too far" as he filled gallon cans with gas Wednesday to tide him over.

"We didn't get much wind here before, and I don't think we're going to get much wind this time," Cary told NBC Bay Area.

Download the NBC News app for breaking news

For a second time this month, there was a run on batteries, flashlights and lanterns Wednesday, said Tom Kenny of Placerville Hardware in El Dorado County.

The store, where a historical marker declares it the "oldest continuously operating hardware store west of the Mississippi River," has sold more generators in recent days than it typically sells in a year, Kenny told NBC affiliate KCRA of Sacramento.

"The size generators that we're selling, we might be lucky to sell one or two a year, sometimes three or four — mostly for agricultural purposes," he said.

Stocks are likely to be scarce well into next week.

Wednesday, PG&E said another round of hot, dry offshore winds this weekend could trigger a third major blackout as early as Sunday "generally north of a Monterey to Yosemite line" — the entire northern half of the state, in other words.

"Details around this event remain unclear, but it has the potential to be as strong or stronger than recent events," PG&E said.

The National Weather Service agreed that weekend conditions could be both worse and more widespread, predicting wind gusts exceeding 60 mph and "critical fire weather conditions."

"Some would say, 'It's life.' But I think it's not the life we used to have," John Sikora of Placerville told KCRA. "I think it could easily be changed."

PG&E is in the largest bankruptcy proceeding in U.S. history, threatened by as much as $18 billion in potential liabilities from the role its power lines played in several highly destructive fires that burned hundreds of thousands of acres of Northern California in 2017 and 2018.

The company has warned that wide-scale rolling blackouts could be needed for as long as a decade as it races to harden its transmission systems, calling it "a multi-year journey."

"We do think that this is the new normal that we need to be prepared for," Ari Vanrenen, a spokeswoman for the utility, told NBC News during the blackouts earlier this month.

At Buzz Thru Joe's in Colfax, the staff worked to get food on ice before moving it to a freezer with power. This is the second time they've had to do it this month. #pgeshutdown pic.twitter.com/wFE8uwVNd8 — Emily Maher (@EmilyMaherTV) October 24, 2019

Bill Johnson, the company's chief executive, said late Wednesday that the company fell behind on upgrading its equipment because the epidemic of destructive wildfires that has afflicted Northern California in recent years took it by surprise.

"The fire risk has grown exponentially, particularly in this region, in the last couple of years," Johnson said at a news conference, adding: "As late as 2017, many people didn't think the risk was high in Northern California. The risk really accelerated."

As early as 2004, however, federal and academic researchers reported that climate change threatened to double the frequency of wildfires, consuming 50 percent more land, in Northern California; they called that the "best-case scenario."

In 2011, more federal and academic research found that a variety of measures projected increases in wildfires associated with climate change ranging from 36 percent to 74 percent by 2085 — with "increases exceeding 100 percent in much of the forested areas of Northern California."

And researchers with the University of Idaho and the U.S. and Canadian forest services similarly reported in 2015 that 17 global climate models predicted sharp rises in the risk of large wildfires through the middle of the century, "with the largest absolute increase in the intermountain West and Northern California."

San Jose Mayor Sam Liccardo said Wednesday that the difficulties facing PG&E are so daunting that he wants to pull the city — the state's third largest, with more than 1 million residents — out of the system, with the goal of setting up the city's own electric utility.

That's the only way to "ensure the distribution of local generation and storage of energy," Liccardo said at a news conference.

Liccardo said he would present the plan to the City Council next week.