We went last year at the end of August. Yes, it is hot and extremely humid, but after going through the hot humid summer here in New England, the relative difference wasn't that great. Even today, the temperature here was 88 degrees with 90% humidity. The best strategy is to get to the parks at opening and do the commando touring in the first two hours. This should get you past most of the E-tickets before the crowds build and it gets really hot. Take a midday break and go for a swim, then return for evening EMH. Be prepared for a downpour at just about any time.
You should also take a lesson from the CM's. If you try to move at a New York pace you will wear yourself out very quickly. Being from the Northeast, I used to get frustrated when the CM's, particularly at the counter service eating spots, seemed to move so slowly. Then it finally dawned on me that they can't move at the pace I'm used to--they'd be an exhausted, sweaty mess within an hour.
Touring in August gave me a new respect for the CM's. While everyone else was sweaty and wilted, they always looked fresh and were good natured. (Perhaps you get used to it living in Florida).
Anyway, we found the crowds to be very manageable, especially following the plans from touringplans.com, and had a great time despite the heat/humidity.