The micro climates in Northern California, Bay Area, usually have the same temperatures in the Winter time, around the mid 50's. The Summer time from the Coastal San Francisco to Sacramento, temperatures can have a 30 to 40 degree difference. In the coolest area of San Francisco it is 54, 7/10/2012 12:45 pm. The warmest is Sacramento where it is currently 96. Fairfield is closer to the Bay Area and it is 94, that is a 40 degree difference which is only 25 miles from the Bay.