I went in September 2017 and not only was it hot it was hurricane season and I was there for Hurricane Irma. After she blew through it was soooooooo humid!! And I am from a humid part of Australia so for me to say that, it was really bad lol
For us, the best time to go is December after Thanksgiving. You get all the Christmas feels but not so much of the crowd. The closer to Christmas though, the busier it gets.
Hope this helps