Hundreds of thousands of Californians were still without electricity due to pre-emptive blackouts Thursday as hot, windy conditions causing wildfires spread south toward Los Angeles, in a situation blasted as "unacceptable" by the state's governor.

Some 540,000 customers in California remained in the dark Thursday afternoon after Pacific Gas & Electric began switching off power the previous day, in a bid to prevent a repeat of last year's catastrophic infernos which killed around 90 people.

Many schools and universities have closed in northern parts of the state and people stocked up on gasoline, water, batteries and other basics, with frustration mounting at blackouts condemned by some as "third world."

Some 600,000 customers in northern California were in the dark after Pacific Gas & Electric began switching off power to prevent wildires
Some 600,000 customers in northern California were in the dark after Pacific Gas & Electric began switching off power to prevent wildires AFP / Josh Edelson

"We're seeing a scale and scope of something that no state in the 21st century should experience," Governor Gavin Newsom said Thursday, blaming decades of "neglect" and "mismanagement" by PG&E.

"What has occurred in the last 48 hours is kids staying home from school, parents that can't bathe their kids," he added. "Folks that come home from work, can't even find a way to get into their garage. You've got people that can't even access water, or medical supplies.

"This can't be, respectfully, the new normal," Newsom said, noting that the current weather conditions were certain to return.

A Safeway grocery store and Starbucks Coffee are closed after the power was shut down as part of a statewide blackout in Santa Rosa, California
A Safeway grocery store and Starbucks Coffee are closed after the power was shut down as part of a statewide blackout in Santa Rosa, California AFP / Josh Edelson

The power cuts enable utility companies to inspect high-voltage lines for damage during particularly flammable conditions caused by high winds and dry vegetation.

Newsom said blackouts were "an industry best practice" under dangerous conditions, but blamed PG&E's failure to modernize its network for the current scale of power cuts.

PG&E defended the shutoffs, telling a press conference that inspections Thursday had found multiple cases of damage that could have caused wildfires had the lines been live.

Patrons sit at candle-lit tables at a restaurant in Sonoma, California, on October 9 during a planned power outage
Patrons sit at candle-lit tables at a restaurant in Sonoma, California, on October 9 during a planned power outage AFP / Brittany Hosea-Small

"We faced the choice here between hardship on everyone or safety -- and we chose safety," said CEO Bill Johnson. "And I do apologize for the hardship this has caused. I think we made the right call."

With high-risk "red flag" winds spreading to the Los Angeles area further south, around 13,000 customers of Southern California Edison had their electricity cut Thursday.

"A number of fires... are burning and there have been structures that have been lost," said Mark Ghilarducci, emergency services director at the governor's office.

A Valero gas station sits vacant after power was shut down as part of a statewide blackout in Santa Rosa, California
A Valero gas station sits vacant after power was shut down as part of a statewide blackout in Santa Rosa, California AFP / Josh Edelson

Fire-fighting planes and helicopters were called in to tackle two fires east of Los Angeles which spread to a combined 900 acres (360 hectares), and were described by officials as "zero percent contained."

The local fire department said multiple structures were destroyed and "numerous medical emergencies" occurred at one of the fires.

Long wait

In the far south of the state, San Diego Gas & Electric warned 30,000 customers living in high-risk areas they could potentially lose their power if conditions worsen.

Urban Los Angeles itself was not expected to be at-risk, although police Wednesday night said they would clear some vulnerable homeless camps.

Several other small fires were reported further north but quickly tackled by firefighters.

PG&E on Thursday had completed inspections on some power lines in its blackout regions, and had restored electricity to more than 228,000 customers by late afternoon.

But others may have to wait several days for inspections before normal service can be restored.

Last November, PG&E's faulty power lines were determined to have sparked the deadliest wildfire in the state's modern history, which killed 86 and destroyed the town of Paradise.

Outdated facilities including vulnerable wooden poles and failure to deforest land surrounding high-voltage transmission lines were blamed for the inferno, causing PG&E to go bankrupt in January.

The company agreed to pay an $11 billion settlement over the devastating wildfires in northern California.

"Those were decisions that were made by Pacific Gas and Electric -- they chose not to modernize their grid," said Newsom. "Over the course of many, many years, it led to their own demise, it led to bankruptcy."

The cost of 48 hours of power cuts could reach $2.6 billion, Michael Wara, an expert in energy and climate policy at Stanford University, told CNN.