I've been to Disney during every season---Jan, April, May, August, Oct., Dec.
My favorite time is early December. But early May and October are really good too. Those times are not as busy as April (Spring break time) or summer (Family vacation time). Of course August is broiling. If you must go during the hot or busy times. just take your time , don't plan to do TOO much on a given day, and be sure to get a Dole Whip ( in the Magic Kingdom --Adventure Land) YUM!