I got used to the fact that December is still pretty mild here in Boston but 55F (13C) is still unusual for this time of year. Right after Christmas I visited Cape Cod for 2 days with my family and because I didn't want to leave my bike behind, I could enjoy spring weather biking in winter, at the waterfront.
What's really nice about cycling at the Cape in winter season is that road traffic is very light. Summer crowds are long gone and those residents who stay here for most of the year move out for winter months anyway. At 6 a.m. you can barely find a single car on the road.