I disagree with most posters so far. Crowd levels are always variable, but my short answer is PM crowds in August are SUPER! After dark hours are your friend!
August is a funny month because many schools go back before Labor Day. More people = more hours, esp for MK, but the timing of sunset also changes between Aug 1 and Aug 30.
Number one variable though is ALWAYS weather. August is prime season for daily downbursts. No downburst = more crowds. Post downburst = less crowds. Storm o'clock is variable. 4-5pm is common. Duration is also rather variable: often 10 min, but sometimes hours. Believe it or not, we've also encountered unexpectedly cool evenings in August! Some afternoons are hotter than blazes. But one trip we wore long pants after dark most of the week! We shivered at the pool! August rain is HEAVY! I suggest quality water-tolerant walking shoes! POST-rain parks are often empty and very comfortable. During lightning pools, all boats, and many rides also close!
IMO, the WORST part of the daily heat is usually 11am-1pm. Every minute gets hotter and more humid. The mistake that many folks make, is toughing out the afternoon heat. Come 5pm, they are exhausted and drenched! (Rain or not)
I suggest keeping a close eye on weather reports!