Pacific Gas and Electric has begun cutting power to more than 800,000 of its California customers in an unusual move to prevent wildfires while its service area is buffeted by severe winds.
The raging winds, referred to as "Diablo winds," will be coming from the northeast with gusts as high as 55 mph.
The utility's decision to curb electricity supplies proactively comes nearly a year after the "Camp Fire," the deadliest fire in state history, killed 86 people and destroyed nearly 20,000 structures in Butte County.
PG&E officials said early Wednesday morning that they had begin shutting off power to approximately 513,000 customers in the areas of Amador, Butte, Calaveras, Colusa, El Dorado, Glenn, Humboldt, Lake, Marin, Mendocino, Napa, Nevada, Placer, Plumas, Shasta, Sierra, Solano, Sonoma, Tehama, Trinity, Yolo and Yuba.
An additional 234,00 customer were due to have their power cut around around noon Wednesday in the areas of Alameda, Alpine, Contra Costa, Mariposa, San Joaquin, San Mateo and Santa Clara. At that point officials said they would consider a third phase of cuts affecting approximately 42,000 customers in locations to be determined.
"The safety of our customers and the communities we serve is our most important responsibility, which is why PG&E has decided to turn power off to customers during this widespread, severe wind event," Michael Lewis, PG&E’s senior vice president of Electric Operations, said in a statement. "We understand the effects this event will have on our customers and appreciate the public’s patience as we do what is necessary to keep our communities safe and reduce the risk of wildfire."
The Diablo winds, similar to the "Santa Ana winds" in Southern California, develop due to higher pressure over Nevada and lower pressure over the central California coast, according to the National Weather Service. The agency also has issued red flag warnings across much of Northern California.
PG&E warned many of its customers they should expect to be without power early Wednesday morning through Friday morning, as weather models show the winds may be the strongest the area has seen in nearly two years.
Southern California may be facing a similar situation, according to Southern California Edison, that region's utility.
Counties currently under watch include Kern, San Bernardino, Riverside and Los Angeles.
San Francisco's BART commuter rail system told riders it doesn't expect a disruption in service, adding that it's been working closely with PG&E for the past several months to prepare for a planned outage. BART said its train operations have the "flexibility to pull power from other sections of our traction power supply system to replace power ... and critical systems such as tunnel fans are also protected by a combination of installed and portable generators."
PG&E said it will continually update customers through calls, texts and emails, as well as via social media and wider media reports.
Customers have been encouraged to stockpile a week's worth of food and water and have plenty of batteries to keep electronics fully charged.
ABC News' Bonnie Mclean contributed to this report.