CFL_Oakland saidThe secret of SF is that the weather is actually incredibly beautiful 9 months out of the year. People just like to whine. Summer temps of 70 will be about right in anyplace that you'd actually want to go (i.e. not the Richmond or Sunset). Bring a light jacket and you'll be fine.It sounds like San Francisco and the Bay Area in general has a very comfortable, pleasant climate.
Generally so, if you can take the constant cold temps. You can always travel a few miles to a warmer spot. I think CFL is in part basing his view on the climate in Oakland, which is mostly warmer in the summer. In San Francisco it is very rarely in the 70's (which I think would be ideal). Normal high temperatures are in the mid to high 60's. If a day gets warmer than that, it almost never stops in the 70's, but gets into the mid to high 80's and above - up into the nineties. That is because the cold wind and fog generally keeps SF in the 60's, and it is only when the wind and fog suddenly stop, that SF gets into the temps of the surrounding area, which are generally in the 80's and above in the summer. For example, for the last few days the high temperature has been in the low 60's, and the wind has almost never stopped. OTOH, winter is mild here - we haven't had a significant frost in SF for about 20 years.
No, people just whine...
In the Mission during the month of May (not the warmest month by far, that's September), there were 9 days where the high temperature was 70 or above (and plenty more in the high 60s). So far in June we've already had two more. I think that's enough data points to refute the misconception that it's "very rarely" in the 70s.
Also, it's usually sunny in the summer (except for the areas west of Diviz/Twin Peaks where most tourists don't go, save the Golden Gate Bridge, of course), and in the sun it always feels a few degrees warmer.
Oakland is downright hot!
My bias, of course, is that I dislike weather where I can't walk quickly or bike at a good speed without getting sweaty. That's 70 or above.