The strongest winds over the next two days are expected in Los Angeles and Ventura Counties, where gusts could reach 65 miles per hour. Light Santa Ana winds were already being felt Wednesday morning.

Southern California has already fought wildfires in recent weeks. Edison’s equipment is a suspected cause of one of the fires, in the Sylmar area of Los Angeles County.

Conditions in the Napa and Sonoma wine country were expected to resemble those from 2017, when wildfires devastated the region in the first of the two major incidents over the last couple of years, said Suzanne Sims, a meteorologist with the National Weather Service.

“It’s just so dry with relatively low humidity,” Ms. Sims said. “This should wrap up by Friday. But there’s another episode of strong winds by Saturday night and Sunday morning.”

PG&E began warning customers on Monday of the growing weather threat, making phone calls as well as sending emails and texts to those who might face blackouts. In addition to the power cuts in the wine country and the foothills, parts of Kern and San Mateo Counties were scheduled to lose power by Thursday morning.

The company has been under scrutiny for its handling of the blackout strategy when it left two million people in the dark Oct. 9 to 12, many without notice. Customers and local governments struggled to get information as PG&E’s website crashed twice and other communications were poorly run.

Local governments said preparations were better this time, but there were still rough edges.

“Power actually went out earlier than expected and caught people a little off guard,” said Amy Ricard, a spokeswoman for Sonoma County. “It’s been a rolling effect,” she said, with various people gradually losing power Wednesday afternoon.