PG&E has begun cutting power in parts of northern California. Nearly 800,000 customers will be affected

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(CNN) - About 500,000 customers of Pacific Gas & Electric (PG&E) in northern California were left in the dark starting midnight on Wednesday when the company began cutting power in an effort to help prevent The start of a forest fire.

Another 300,000 customers will lose energy later in the day, which will add a total of 800,000 customers affected by the measure, said Sumeet Singh, vice president of the company's Community Fire Safety Program.

Several school districts and an important university have canceled classes, while transit tunnels and public transportation services may also be affected, authorities said.

Forecasters warn that many parts of Northern California are in extreme fire danger, with a forecast of windy and dry conditions.

"We implemented this public safety power outage as a last resort," Singh told a news conference on Tuesday.

It could take several days to restore power, Singh added, as the company will first conduct safety inspections once the generalized wind event is over.

PG&E has been criticized in recent years for the role of its team in a series of catastrophic forest fires throughout the state, including the deadly Camp Fire 2018. The company has agreed to pay billions of dollars in damages.

Who will be affected

The power outage was scheduled for this week in stages, PG&E said in a statement Tuesday, "depending on the local weather conditions, starting with counties in the northern part of the state."

On Monday, San Jose Mayor Sam Liccardo urged residents to prepare to run out of electricity for seven days.

The closure will cover portions of 34 counties in northern, central and coastal California, he said.

The California Department of Transportation has been working with the utility company to secure backup power generators to keep the Caldecott Tunnel open in Contra Costa and Alameda counties and Tom Lantos Tunnel in Pacifica, spokesman Bart Ney said. to CNN.

The Caldecott tunnel would close on state route 24 and the Lantos tunnel could close along state route 1 in Pacifica, said CNN affiliate KGO.

The Bay Area Rapid Transit (BART) system is not expected to be affected by the shutdown, he said in a tweet. BART has portable generators at certain stations and will have personnel monitoring the generators.

Some stations may have interruptions in escalators, BART said.

School officials canceled classes on Wednesday in anticipation of closing. Closures affect all schools in the Napa Valley Unified School District, the San Leandro Unified School District and the Cloverdale Unified School District, in addition to the Bennett Valley United School District schools in Strawberry and Yulupa.

UC Berkeley also canceled the classes in response to the power outage. The campus will be open on Wednesday, but services will be limited, the university said.

The Governor's Office of Emergency Services has activated the State Operations Center to help affected counties in the closure, he said.

"Cal OES Fire, Law Enforcement, Inland Region and Coastal Region personnel are currently working with various response agencies to address all emergency management, evacuation and mutual assistance needs," the agency said in a statement from press.

Why weather conditions are important

The conditions that are forecast for parts of the state "have historically led to catastrophic forest fires," said senior public service giant Evan Duffey, a meteorologist at the press conference.

And this, he said, according to all parameters "is expected to be the strongest offshore wind event since October 2017".

The National Meteorological Service warned of high winds and low humidity on dry vegetation, which according to the service acts as "fuel".

"This is a recipe for the explosive increase in fires, if a fire starts," the weather service said. "Have your backpack ready."

The service issued red flag warnings starting Wednesday morning in the mountains and valleys of North Bay, the hills of East Bay and the valleys of East Bay. The warnings mean that "warm temperatures, very low humidity and stronger winds are expected to combine to produce a greater risk of fire," the service said.

The strong winds will begin on Wednesday morning and will last until Friday morning, Duffey said during the press conference.

It could take days to restore power

PG&E has activated an emergency operations center that has staff at all hours, Singh said.

Some of the clients of the utility company may disconnect "even though the weather conditions in their specific location are not extreme," he said during the press conference.

"(That's it) because of the interconnected nature of our power grid and the power lines that work together to provide electricity to cities, counties and regions," said Singh.

And the electricity will take several days to recover while the company inspects its equipment to make sure there is no damage, he said.

"We understand very much the inconveniences and difficulties that a power outage would cause and we do not take or make this decision lightly," he said. "This decision ... really focused on ensuring that we continue to maintain the safety of our customers and our communities."

PG&E said earlier that it is "likely" that his team started Camp Fire 2018, the deadliest and most destructive fire in the state, when a power line touched nearby trees. The California Department of Forestry and Fire Protection found PG&E responsible for the fire, which killed 85 people and destroyed thousands of structures.

The utility company announced in September that it had reached a $ 11 billion deal with insurance companies for claims arising from the devastating forest fires of 2017 in Northern California and Camp Fire. In June, PG&E paid 1,000 million in damages to local governments for fires linked to its power lines, poles and other equipment.

CNN's Carma Hassan and Joe Sutton contributed to this report.