The forecast poses a higher risk for damage and sparks on the electrical grid, which could contribute to "rapid wildfire spread," Pacific Gas and Electric Co. said in a statement.
About 179,000 customers in 17 counties in Northern California will be affected by the public safety power shutoff, or PSPS. The shutoffs have begun in waves in different counties, with the first shutoffs happening at 2 p.m. local time.
The peak high-winds period should end around noon Thursday in the Sierra Foothills, North Bay and San Mateo County and by noon Friday in Kern County, according to PG&E.
After the high winds subside, technicians will inspect the de-energized lines to ensure they weren't damaged and restore power as quickly as possible. The "vast majority" of customers should have electricity within 48 hours after the weather passes, according to PG&E.
Southern California Edison also announced Wednesday afternoon that more than 308,000 customers could have their power cut, and San Diego Gas & Electric may cut power to 23,944 customers.
Officials said at a Wednesday evening press conference that someone intentionally fired a pellet gun through the windshield of a PG&E employee's car in Glenn County.
PG&E began warning customers on Monday about the possibility of the second deliberate blackout this month.
The heavy wind gusts during the last PSPS, which affected more than 2 million people, caused more than 100 instances of serious damage and hazard on PG&E's distribution and transmission lines.
In Southern California, the deadly Saddleridge Fire ignited on Oct. 10 near an electrical transmission line operated by Southern California Edison. The company had shut down some of its power lines, but not the one running through Sylmar in Los Angeles County.
"The sole purpose of PSPS is to significantly reduce catastrophic wildfire risk to our customers and communities," PG&E officials said in a statement on Monday. "We know that sustained winds above 45 mph are known to cause damage to the lower-voltage distribution system and winds above 50 mph are known to cause damage to higher-voltage transmission equipment."
The announcement of the most recent blackout drew ire from community members who criticized the power company for not working to find alternative solutions sooner.
PG&E spokeswoman Tamar Sarkissian told ABC San Francisco station KGO that it's installing devices to divide the grid into smaller segments so blackouts are targeted in smaller areas.
The company aims to end PSPS events within the next 10 years, PG&E President and CEO Bill Johnson said before the California Public Utilities Commission on Friday.