I visited SF for the first time in December and at first I didn't realize why people were complaining about the cold when it was rather nice weather outside (I'm from 60 degrees north) and the weather was in the 60-70 Farenheit range (20 celsius) which I consider to be nice and temperate climate.

But after a week it hit me. It's cold as hell indoors! I have warmer in my house now than I had in my hotel room or office and it's snow and ice outside.