It might always be cold where you are in January, but in past years I would make a point of wearing shorts on New Year's Day--it was always warm enough! But not 2013. Nor 2012 for that matter.
It's been cold enough for ice to become a danger even in Southern California this week (a friend of mine slipped on ice and broke her leg yesterday!) and the Indoor Air Quality Association has some great information for you about your indoor environment during cold weather in this video. It's supposed to warm up after today. We can only hope!
Stay warm and don't light your fireplace today in the Bay Area--it's a no burn day!