High winds and dry conditions have prompted a National Weather Service red flag warning for elevations 1,000 and above in the North Bay from 10 p.m. Sunday to 8 p.m. Monday.
The services says inland peaks in Napa and Sonoma counties are particular areas of concern, where north-northeast winds of 15 to 25 mph and gusts of 30 to 50 mph are expected Sunday night.
While wind speed is expected to ease by Monday, conditions will be drier, with relative humidity will drop from 30 to 40 percent to 10 to 25 percent.
Mild mountain temperatures of 55 to 65 degrees are forecast overnight Sunday.
"The combination of the offshore winds, lowering relative humidity values, and dry fuels will likely lead to critical fire weather conditions for the higher elevations of the North Bay," the NWS said in an advisory.