San Francisco in July!
Are you talking about in general, or as part of trips?
For the latter, beautiful Moline, Illinois, staying at the now deservedly-defunct airport Hampton Inn. Was -8 F (with a wind of about 20 mph) when the shuttle took me to the airport at 4:30 am.
Ugh.
Coldest that didn't involve a trip (I was living there for the year) was -22F in Chicago in January 1978. (It set the record for coldest day ever in Chicago).