LIVE: Here's a look at real-time temps around Bay Area
"Temperatures could reach 110 degrees in places like St. Helena, Fairfield, Walnut Creek and Livermore," said ABC7 News Meteorologist Mike Nicco.
Conditions could become life-threatening in some inland neighborhoods, which are expected to be the warmest.
"This all goes through 9:00 tomorrow evening," said Nicco.
Nicco says high temperatures could break records in Concord, Livermore, San Jose, San Rafael and Santa Rosa.
RELATED: Watch the latest AccuWeather forecast
San Francisco and other cities along the coast are not under a heat advisory, with temperatures expected to be slightly cooler in the 70s and 80s.
The extreme heat has prompted a Flex Alert for Thursday, as much of California and Nevada are experiencing sweltering temperatures.
The big focus is on conserving energy between peak hours from 5 p.m. to 10 p.m.
Nicco also warns people who are sensitive to air quality conditions to stay indoors. A Spare the Air alert is in effect, with high concentrations expected to form in the North Bay, the inland East Bay and the Santa Clara Valley.
"Today is the hottest day in the forecast, but the heat's going to hang around through at least Saturday," said Nicco.
More 100s on are expected on Saturday before the weather starts to cool off.
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