Just a side note from someone who has only visited the area a few times. Take this for what it is worth.
People from that part of the world have no idea what winter is. I have visited S.F. in the winter a few times and the weather was lovely although sometimes wet. A lot of the locals were bundled up like they were on a polar expedition and complaining like crazy. We were in shorts and tee shirts much of the time and loving life. A long sleved tee shirt and a windbreaker was the most I needed.
Bear in mind that I am not from a particularly cold area (Baltimore, Md).
Even if it is exceptionally cold for the area the temps will still be nice. There may be rain though.