The advisory is in effect from 11 a.m. until 7 p.m. Thursday and Friday.
VIDEO: Here's your ABC7 AccuWeather forecast
ABC7 News Meteorologist Mike Nicco says temperatures will be 10 to 15 degrees, maybe even 20, above average everywhere except the Coast.
That will increase our risk of heat-related illnesses Thursday, Friday and Saturday.
But there is relief on the way. There is a 33 percent chance of temperatures below average for the first couple of days next week before the heat returns.
A Spare the Air Alert is also in effect for the Bay Area through Friday.
Watch the latest AccuWeather forecast and take a look at recent weather stories and videos.