Fall and Spring are both IFFY in my book. DH and I are from the south and we do not like to swim when the breeze is cool, even though the pools are heated I have never felt one that felt warm to me and when you get out you freeze. I would say October is okay most any year, but once you get into November and December you will just have to play it by ear. Of course some people will swim even if it is 50s or 60s outside, it just depends on what your tolerance level is. For us, anything below 80 air temp is almost too cool to swim. It has been in the 70s here the last few days and while it feels great we are not going to the neighborhood pool (and no one else is there either, although they say it is heated.) At water parks you have to get out of the water to climb the slides, etc., and we would not enjoy this if it was cool. One more good reason to do Disney in the summer for us. Even last March was chilly when we were there, but it can change from day to day during your stay.