researching this subject:
it seems motorcycles are usable from about 40F to 90F with optimum range being 60F to 80F
below 40F the risk of slipping on ice becomes a concern even if you have state of the art electrically heated gear to keep you warm
above 90F the risk is getting stuck in traffic sitting on top of a hot engine with no airflow to cool you down.
with this in mind if we look at Atlanta:
then it is pretty much perfect. You will have some times when it is too hot and some times when it is too cold but MOST of the year will be ride-able.
Florida is SLIGHTLY better as there would be NO days that are too cold to ride but there would still be days when you can’t ride due to rain for example, plus you still need a car for grocery shopping and so on …
so the goal isn’t a state where you can replace a car with motorcycle ( you can’t ! ) but rather a state where you can get enough use of a motorcycle to not have it completely useless.
here in NJ you probably wouldn’t ride from November to March by which time you would have to learn how to ride all over again …
in Atlanta would have some good afternoons in January and February and some good mornings in July and August … so you would be able to maintain your riding skills year round …