Elevations higher than 1,000 feet in Napa County may be conducive to wildfires from Saturday night into Monday night, according to the National Weather Service.
The warning is in effect for other parts of the Bay Area, but higher elevations in Napa and Sonoma are under the greatest threat, according to officials. The driest conditions and strongest winds are anticipated there.
Red flag warnings indicate that there are strong winds, low humidity and warm temperatures. Fires that develop would likely spread rapidly.
Officials expect northeast winds from 20 to 35 miles per hour with gusts from 45 to 60 miles per hour.