A strong high pressure ridge is expected to send temperatures rising around the North Bay on Monday, with a high of 94 forecast in Santa Rosa, the National Weather Service said.
Ukiah will break into triple digits at 101 degrees, the forecasters said, with a high of 99 predicted for Tuesday.
Napa will hit 95 today; Lake Berryessa 98, forecasters said.
On Tuesday, Santa Rosa is expected to drop a bit to 89, followed by daytime highs in the 70s for the rest of the week.
The record temperature for Santa Rosa on Oct. 1 is 102, reported in 1970 and 1980.
The Weather Service said there could be record high temperatures across the state Monday afternoon along with gusty winds in the mountains and extreme fire danger.
The Bay Area Air Quality Management District has issued a Spare the Air alert for Monday. Officials are asking residents to avoid using their cars to get around.
Inland valleys in the Bay Area could see triple digits. Downtown Los Angeles could hit 100, matching a daily record set in 2008.
On Sunday, L.A.'s Woodland Hills area hit 103, topping a record set in 2003. Indio had a low of 81, breaking the previous record for warmest low temperature of 79 set back in 1966.
The weather service says there's high fire danger through Tuesday in mountains because of hot, dry weather, tinder-dry brush and possible wind gusts of 20 mph or more.
The heat could start to ease Tuesday evening.