Pacific Gas and Electric has expanded its power blackout zone to 940,000 customers across Northern and Central California as extreme weather forecasts threaten to increase the risk of wildfires.
The projected wind gusts of up to 70 mph, combined with dry vegetation, create prime conditions for wildfire.
"Winds of this magnitude pose a higher risk of damage and sparks on the electric system and rapid wildfire spread," PG&E said in a statement. "The fire risk is even higher because vegetation on the ground has been dried out by recent wind events."
The planned power outages will affect roughly 90,000 more customers than previous estimates by the utility. Over the course of two to three days, the shutoffs could leave more than 2.5 million people in the dark.
"Charge any devices you might need, have water and nonperishable foods at your disposal, and if you have special medical needs, please be sure to have access to support and resources," PG&E's President Andy Vesey said Friday.
Dry, hot and windy conditions were expected to hit the region between 6 p.m. and 10 p.m. Pacific time Saturday and last through Monday afternoon.
"This wind event is forecast to be the most serious weather situation that Northern and Central California has experienced in recent memory," said Michael Lewis, PG&E's senior vice president of electric operations.
When compared to the conditions that fueled the deadly October 2017 wildfires that ripped through Northern California, these winds not only have the potential to be stronger but also the potential to last longer, according to National Weather Service meteorologist Steve Anderson.
"The peak winds during the wildfires in the North Bay in 2017 only lasted four to 6 hours," Anderson said. "These wind speeds — we're looking at a range of 24 to 30 hours."
The planned shutoff is the largest intended to prevent wildfires since PG&E started conducting "public safety power shutoffs" in a handful of counties last year.
The power shutoffs will roll out in six phases, but the utility said times may change depending on weather conditions. The first round of shutoffs were expected as early as 2 p.m. on Saturday, but were delayed, according to PG&E during a press conference Saturday night. The utility said it shut off power in areas of the Northern Sierra Foothills, the Northern Sacramento Valley and the North Bay Area at 5 p.m.
Power shutoffs for the rest of the planned Bay Area regions began around 8 p.m. on Saturday, which were previously scheduled for 5 p.m.
The utility planned to cut power in 36 counties across parts of Humboldt, the Sierra Nevada foothills, Western Sacramento Valley, and every county in the Bay Area except for San Francisco. A sixth phase is scheduled for Kern County on Sunday morning.
PG&E says it hopes to begin the process of restoring power on Monday.
Two large wildfires drove California Gov. Gavin Newsom to declare states of emergency in Sonoma and Los Angeles counties, which will help communities get state aide.
The Kincade Fire in Sonoma County has burned nearly 25,500 acres since it started Wednesday night, and in northwest Los Angeles, the Tick Fire has burned 4,600 acres.
The state's largest utility is opting to shut down power lines as a precaution against conditions similar to those that fueled some of California's most catastrophic fires. NPR previously reported that although the power utility had informed regulators that part of a transmission tower broke not far from the Kincade Fire shortly before it began, it's not yet clear whether PG&E's power lines are to blame for sparking the fire.
State fire investigators found PG&E's electrical lines responsible for last year's Camp Fire in Northern California, the state's deadliest wildfire, that killed 85 people.
The fires also prompted billions of dollars in lawsuits and wildfire liabilities that drove the utility to file bankruptcy.
Gov. Newsom announced on Friday that the state would allocate $75 million to support communities with funding for emergency services, power generators and other public health and safety needs during the power outages.
On Saturday, Newsom reiterated criticism of PG&E that he made in a press conference a day earlier - he blamed the utility for prioritizing profit over public safety and condemned the company's refusal to modernize its grid.
"The impact of [PG&E's planned power outages] is unacceptable," he said in a video posted to Twitter. "We've got to hold them accountable."
Reporter Jeremy Siegel and digital producer Audrey Garces are with NPR member station, KQED.