Windy and dry conditions pose an increased risk of wildfires Friday, according to the National Weather Service.
Forecasters say the fire danger will go up as strong winds engulf the Bay Area beginning Thursday, drying already arid land and dropping relative humidity to dangerously low levels.
The warning comes shortly after the service issued a wind advisory Wednesday for the North Bay's interior mountains and East Bay hills in effect from 11 p.m. Thursday through 2 p.m. Friday.
The strongest winds were expected early Friday morning, with gusts reaching 40 mph in southern Napa County and in Stockton and about 30 mph in most other areas of the region.
Humidity levels are expected to drop below 20% in most areas by Friday afternoon, except for along the coast where they will be about 30-40%.
Find the latest forecast and more weather information on our weather page.