With strong, dry winds expected to tear through vast portions of California on Wednesday, the power supply to more than 800,000 homes may be turned off by Pacific Gas and Electric as part of an effort to reduce the risk of wildfires.
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.
The raging winds, referred to as "Diablo winds," will be coming from the northeast at 20 to 30 mph, with gusts as high as 55 mph.
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.
"This is shaping up to be one of the most severe dry-wind events we've seen in our territory in recent years, and we want our customers to be prepared for an extended outage that may last several days," Michael Lewis, senior vice president for PG&E Electric Operations, said in a statement. "We want our customers to be aware that, based on this number, it could take several days to fully restore power after the weather passes and safety inspections are completed."
PG&E noted that customers in the nearly 30 counties -- Alameda, Butte, Contra Costa, Napa, Placer, Santa Cruz, Santa Clara, Sonoma among them -- could be affected.
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.