We went 12/14- 12/19 last year and although it was nice when we arrived and we were wearing shorts and stuff, the nites got cool and 2 or 3 days into the trip the temp's dropped into the 30's!!!!!!
We wore layers upon layers and needed gloves it was that cold!!!
: Also by the time we left Florida, it was started to warm up.
It all depends upon when you go I guess and what the weather has in store for you.
So be prepared for anything and pack warm clothes, gloves, hats if needed.
I suspect if you are going Early Dec, it will be very nice.