CONCORD, Calif. (KRON) -- A red flag warning issued by the National Weather Service goes into effect at 11 p.m. Thursday and will continue into Saturday. Most of the San Francisco Bay Area falls under the warning, which is due to the critical fire weather conditions brought on by heavy wind, low humidity and dry fuels. Dry offshore winds are expected to kick up Thursday evening, according to KRON4 Meteorologist John Shrable. “With these strong offshore winds comes a major increase in fire danger as humidity drops along with gusts as high as 40 mph,” Shrable said. Isolated gusts of up to 65 mph are possible in the highest elevations, according to NWS. Marin County vegetation fire sparked by electrical issue: officials Daytime relative humidity is forecasted to be as low as 10% in red flag warning zones, weather officials said. Graphic: Kyla Grogan To prevent potential wildfires, approximately 8,000 Pacific Gas and Electric Company customers in Bay Area counties may lose power, the utility announced Thursday. The “duration and extent” of the proactive shutoffs will depend on weather conditions in each area, and not all stated customers will be affected throughout the red flag warning, PG&E said. PG&E released the approximate number of customers that may be affected in each Bay Area county as of Thursday morning: Alameda County: 422 customers Contra Costa County: 973 customers Marin County: No proactive shutoffs announced Napa County: 3,103 customers San Francisco: No proactive shutoffs announced San Mateo County: No proactive shutoffs announced Santa Clara County: 663 customers Solano County: 1,838 customers Sonoma County: 1,010 customers PG&E customers can use the Public Safety Power Shutoff advisory website to determine if their location is at risk of a potential shutoff. The utility said that shutoffs may begin as early as Thursday morning. Officials remind people to be aware and to avoid using things like lawnmowers and weed trimmers in the middle of dry vegetation, and that includes parking a hot car in those dry areas. PG&E said it understands customers’ frustration and is working to avoid future power shutoffs by undergrounding 10,000 miles of lines. Critics have said that the power utility may be better off insulating its overhead powerlines and seeking help from state officials. The red flag warning is set to expire at 5 p.m. Saturday.