Christmas, late December & January… and weather is at its coldest in the Northern Hemisphere… so even some “warmer” places will not be hot. Just so you are aware…
You pretty much have to get down to about 25 degrees North Latitude (ie Naples to Fort Lauderdale line) to see nice balmy weather on the Atlantic Coast… averaging in the 70s or higher.
Places on the Pacific Coast… like Seattle, San Francisco, even a great deal of California tends to have even cooler average temps at that time of year than Florida !!
As does US interior Destinations like Tucson…
All of them can see temps in the 40s, 50s, and 60s.
Hawaii would be a good choice, as they average in the 70s as well at that time of year.
Mr TTR & I travel most Christmases… and we’ve seen it all… including SNOW at the Florida Border.
(My Dad who is retired and winters in Southern Florida, says he’s seen freezing temps / frost even further south in the State)
As I say you have to go pretty far south into Florida to have a higher guarantee of decent weather (the ONLY place in Florida by the way where it has never gotten below freezing 0 C = 32 F is the Florida Keys)
Which is one reason that we often make it a Destination of Choice for us during any month in the Wintertime… either flying in to Key West, or driving down from Canada.
It has weather that is very Caribbean like… without the added expense.
Mind you… the Northern Caribbean (Greater Antilles Islands)… are going to be still impacted by any Northern Cold Fronts (dip in the Jet Stream)… in which case you won’t see temps in the 80s…
And they can be even chilly… or greatly effected by wind & rain.
You truly have to go to the Lesser Antilles Islands… or the Southern Caribbean Islands off of South America to see the more tropical “GURANTEED” good weather in the prime Winter months…
Hope this helps,