I am guessing it is about a 10 degree difference easy.
Have a Beautiful Day!
It's not a matter of agreeing....it's a scientific fact that winter temperatures in south Florida are considerable warmer that central and north Florida locations. To take this one step further, Key West winter temperatures are higher than south Florida temps...another scientific fact.......
Florida is a very long state! Up north, in Jax, they get very cold in winter relative to the southern part of the state, and each city further south gets a little bit warmer as you go. I have been involved in a snowball fight in St Augustine, but here in Key West we can say we are the ONLY city in the continental US that has never seen frost, so you can see there's a big difference as you move south. The Gulf of Mexico is also shallower and generally warmer than the Atlantic Ocean, so I think the west coast is a bit more protected from cold than the east coast of Florida. If warmth really matters, you might want to consider the American Caribbean, here in the Florida Keys! (I wrote a recent blog on that very topic: http://www.trulia.com/blog/jim_olive/2012/09/key_west_real_e )
Best of luck with your purchase. I was born in Fort Myers and lived in Cape Coral for years, so I know those are good choices as well...Jim