Zone 8? Nope, SF rarely gets below freezing so 10a is quite accurate. They are often in fog and don't get the day time heat I get further north and more inland but they can grow all kinds of frost sensitive plants, The SF Botanical Gardens are to die for, growing many South American tropical and Australian plants..
@Moonhowl, that last link you provided says " San Francisco is in zones 10a (with a range of 35 to 40 F) and 10b (range of 30 to 35F).".
