The National Weather Service has issued a red flag warning for higher elevations in the North Bay, East Bay and Santa Cruz Mountains, taking effect at 1 p.m. Thursday and lasting until 6 a.m. Saturday, officials said.
A heat advisory also has been issued across the entire Bay Area from 11 a.m. to 8 p.m. Thursday, weather officials said.
Red flag areas in the North Bay include in and around where the 51,000-acre Glass Fire is burning. The warning lends additional urgency to the ongoing firefight.
"While not expecting the same critical fire conditions as what was observed earlier this week, critically dry and breezy conditions are expected in the area," the weather service said.
Separately, Cal Fire officials said that on Sunday, the first day of the Glass Fire, two firefighters had to deploy fire shelters while battling the blaze in Napa County.
Cal Fire officials said "intense fire conditions, fueled by gusty, off-shore winds" forced the firefighters "to take refuge … in the aluminized cloth tents that offer protection by reflecting radiant heat and providing a volume of breathable air."
Neither firefighter was injured, though several transport vehicles were damaged, Cal Fire officials said. No further details were immediately available.