We have gone the last 3 years, the 1st week in May. It is hot and humid in the afternoons,especially,but the crowds were very manageable with fast passes and planning. We ran into a lot of large high school and jr.high groups, but they only affected the rides, shows, or cs they were at. We just headed a different direction.They also did not seem to use fast passes.Also, watch out for Grad days ( I think that is what they called it)as they closed MK early during our stays. This year we also went in Jan. and August. Jan. was very comparable crowd wise other than the school groups. and August was very hot and very crowded, but we still had a great time.