August is very hot (90 to 95 degree) but the humidity is what kills you. There will be thunder storms generally around 3:30pm every day. The rain comes and goes quickly, sun's back out and everything is back to normal by 5pm. We frequent the water parks more in August, and we make sure that if we're going to the theme parks, we do am rope drop. We head back to the villa around 11:30 and head back out after 4pm. The sun is the worst from 11 to 3, and combined with the humidity, it beats you up.
A little dip in the pool before or after lunch helps break up the hot day at the park. AM rope drop is also the time to see the animals at AK, in the afternoon they just sleep and hide in the shade!
Crowds will be a little less than in July because Florida schools head back a round the 13th+/-. However, crowds will still be high because Europeans don't mind the heat and they vacation a lot in August.