I want to go to Europe between Christmas and New Years. What country would be the warmest at that time?
You can't sort it by country - - you have to do it by region by taking samples of cities with reporting/observation stations. Using something like seasonal averages on wunderground.com will do the trck. For example, think of Italy: it would be warms as heck around the Gulf of Taranto, but pretty nippy in the alps.
Just go as far south as you can. Put your finger on Florida and follow it around the globe. Puts you in the Med. Most of Europe is much further north than the US so it will be harder to find south Florida type of weather if that is what you are looking for. Need a better idea of your actual interests besides warm weather.
We want to hike, sightsee - not sit on a beach. I broke my arm this last June and am still recovering so can't go where it is winter-like.
The Florida trick doesn't quite work. Its most northern border is at about 31N. Tarifa (36N) is at about as far south in Europe as you can get without counting Crete or something. A degree of latitude is sixty nautical miles which is about seventy statute miles, so there's about a 350 sm difference - - about the difference between Washington, D. C and Portland, Maine.
Take a look at the Algarve. There are plenty of good hiking areas in the interior as well as along the coast.