San Francisco is about to close out summer with one of its hottest stretches of the season and a twist that could bring thunderstorms before fall officially begins. A complex pattern of building high pressure, offshore winds and incoming tropical moisture will drive a three-day warm spell from Monday through Wednesday, with daytime highs climbing into the 80s and a few neighborhoods pushing toward 90 degrees. Read the rest of the Bay Area weather forecast at the link in our bio. #cawx #californiaweather #sanfrancisco #bayarea #heatwave