I'm an Annual Passholder at Disney. I feel for people who have to come in the summer, and are not used to the heat, or don't know how to deal with it. At least if it's really miserable, I can come home and go back another day.
Absolutely, I'm also an annual passholder and the perk of that you can leave the park if it's too hot or vice versa, because just stepping aside just to another location area can really be totally different. Sometimes where you thought would be harsh is not and actually is where you was before choosing to go to where you didn't think was a good idea!
It's not easy if you never experienced that kind of humidity or temperature before or even if your from another part of the world and not use to magnitude strong AC from indoors. As a Floridian you let go to complain about heat because you can always cool off somewhere which is better than winter when it's cold and rainy and windy and if your lucky indoor places and transportation won't put heat which is not better and people can be more sick.