We were there last August - we had to reschedule and that was the only time for us to make it. We actually did not think it was that bad. We are from the Northeast so heat and humidity is normal for August, but normally we wouldn't be walking outside all day long. However, for us, we were just so happy to be out and relaxing after such a hard 2 years, we didn't care about the heat! The kids loved the pool time and we just took it easy if we got too hot.
We also did not have a long wait at really any rides and we did all the parks. Longest wait was Minnie and Mickey's runaway railway. We don't do all day long park - we usually take a mid-day pool/relax break.
I would go in August again to avoid crowds, but I think this year is going to be wild because so many people had to postpone and reschedule trips.