The utility says it turned off electricity Saturday morning in portions of Napa, Solano and Yolo counties.
PG&E is under enormous pressure after downed power lines and other equipment have been blamed for previous devastating fires.
The company also may cut power to 30,000 customers in Butte, Yuba, Nevada, El Dorado and Placer counties.
The National Weather Service is reporting strong winds, including gusts to 50 mph (80 kph) north of Sonoma.
A wildfire that broke out Friday in Stanislaus County grew to 600 acres (243 hectares) but Cal Fire says it’s 75 percent contained.