The heat is almost unbearable but if you realize it may be theonly time of the year you can go (shedules, kids, etc.) then that is a comfort.
Go out early and come back to your hotel and/or pool in the afternoon to refresh then go back out in the early PM. The afternoons are hot but not as humid. At night the humidity takes over. Don't expect the temperature yo go below 72. But it will get into the low 90's with heat indexes approaching or going over 100. One year we went, the heat index was 122 (yikes) and we were on Main St. for the parade. I'm not trying to dissuade you from going but realize you have to deal with it. Expect a shower at 4-5 PM every day. Sometimes it will cool off after that, sometimes more humid.
My favorite time is November (warm days and cooler nights)
The crowds in August are not that bad - Florida is back in school by then.