I went in Aug in 2004 ,,hot-hot hot,,,but the crowds were lower and those mickey bars reallllly helped.
We found spending time early in the morning and late in the evening in the parks best. We took naps in the afternoon or hung out at the pool.
Misty fans are great and scheduling adrs in advance helped ---but a side note we ate far less due to the heat. If I went again in Aug I'd make sure I had a case or two of water ordered .
Have fun and stay well hydrated.