Well, a lot of the time it is quite a bit warmer in Hyannis in the winter than even just north of the canal. Hasn't been true the last year or so, but generally you can ride quite easily there all year round, as they really don't get as much snow and the temperatures are moderated by the ocean. So, while it might be 30 or 25 by me, it will be 40 there. I think that's a good temperature for running!
But Miami in January sounds good, too, but probably not enough time to train for a marathon?