Those two months are the best summer you'll find anywhere. When I moved to SF, I missed them dearly. SF summers are terrible, and I found three of them more depressing than seven rainy winters in Seattle ever were.

I'll also take nonstop rain from Nov-Feb any day over the snowy winters in the Midwestern states where I grew up.

Finally, the key to not letting your plans get ruined by rain is to always plan for the possibility of rain. =)