Sonoma County does produce excellent wines, but I haven't had the opportunity to visit the producers. Driving out of the Bay area across the bridge and into Sonoma-Petaluma one feels a great change in environment, as if one can breathe more freely (one of those changes that PoppaGator mentions).

I guess I was lucky, I remember fog in SF just once, and I was staying in Palo Alto at the time (it was sunny there). My visits were mostly from Fall to Winter. August days are usually fine.

Point Reyes beach area (post by Joe, above) is great.