We can't compete with the newsworthy raging snowstorms and sleet back east, but we do get the occasional frost and even, rarely, a bit of snow (which doesn't stick).
This photo of Villa Ragazzi's vineyard, newly removed, was taken the day after Thanksgiving 2014. That white stuff is early morning frost on the ground. Our first citrus-threatening freeze came on Christmas Eve. Nothing much to report since then.
Now throughout the Napa Valley vines are starting to grow, precociously, and vineyard managers are testing their frost protection systems. Those tender young shoots won't be safe until early May.