Got home [San Ramon] in time for a Bar-B-Q at a friends house---no fog for them, high in the upper 90's!!---so they'd all gone swimming, while we were in the cool fog-shrouded city!! Yes, that's one of the familiar & cool facts about visiting SF, going from weather temps in the 90's [or even 100's!!] to the cool 60's, just by crossing a few mtns and bridges---really cool stuff, but really hard to make visitors/tourists believe. Answer--always bring a jacket or sweatshirt, just to be safe and comfortable!!