As others have said, it's hot, humid, and crowded. BUT you're at Disney, so that eases some of the pain, right? Our previous trips have been in June, and we always experienced an afternoon thunderstorm/shower almost every day. They don't last long (20 min. up to an hour). On the occasions it lasted longer, or more than one shower kept popping up, we tried to find indoor shows or rides. The parks will clear, but we always stayed because I'd rather be a little wet enjoying fun things at the parks than dry in my hotel room. One thing you might consider is bringing ponchos with you. They're pretty inexpensive, roll up easily, and can be tucked in a backpack or a stroller. We would spread them out once we were back in the hotel so they could dry, roll them up tightly for the next day, and we were ready once again. Another thing that's helpful is a cheap little fan. We found some for around $1 that were very small and light weight, but gave just enough breeze on the neck to make you feel better. As others have said, hit the park at rope drop to get there while it's coolest.