Prompted by forecasts of powerful winds, PG&E confirmed that public safety power shutoffs for 940,000 customers across 36 counties will start at 2 p.m. Saturday and proceed in six phases.
All Bay Area counties except San Francisco will have outages, and about 400,000 customers in the region could lose power.
The utility initially estimated that 850,000 total customers would be affected, but increased that number by 90,000 on Saturday to 940,000.
PG&E said customers should prepare for shutdown lasting 48 hours or longer, because lines must be inspected before power can be turned back on.
The shutoffs will take place in six phases.
The first counties to be affected, at 2 p.m., will be Amador, Butte, Colusa, El Dorado, Glenn, Nevada, Placer, Plumas, San Joaquin, Sierra, Siskiyou, Shasta, Tehama and Yuba.
The second phase about 4 p.m. will impact customers in Lake, Marin, Mendocino (south), Napa, Solano, Sonoma and Yolo counties.
Phase three will start about 5 p.m. for customers in Alameda, Contra Costa, Monterey, San Benito, San Mateo, Santa Clara, Santa Cruz and Stanislaus counties.
The fourth phase will start at 5 p.m. for Alpine, Calaveras, Mariposa and Tuolumne counties.
Phase five will start about 5 p.m. for customers in Humboldt, Mendocino (north) and Trinity counties.
The sixth and final phase will be at 10 a.m. Sunday for Kern County.
Customers can determine if their address may be impacted by using the lookup tool on the PG&E’s website.
PG&E officials said that forecasted high winds and dry air could be one of the most powerful wind events in Northern California in decades, with widespread winds of up to 60 mph and gusts reaching up to 70 mph in higher elevations.
The shutdown could be larger than one that began on Oct. 9. Eventually 738,000 customers in 34 counties lost power at some point during that outage. PG&E was widely criticized for its handling of the event, including for poor communication with customers and local governments.
PG&E has been shutting off power proactively to prevent wildfires after utility lines started massively deadly and destructive fires over the last two years. PG&E has estimated that similar power shutoffs may be necessary for the next decade until the utility can upgrade its technology.
But despite a power shutoff in Sonoma County on Wednesday night, an investigation has begun into damaged PG&E equipment found near the origin of the Kincade fire.
The blaze had grown to more than 25,455 acres and destroyed 49 structures as of Saturday morning and was only 10 percent contained.