If anything, the weather in August (and especially in September) may be a little worse than early July.
It may also be, however, that it's just my impression from living here. In June and July, it's just hot; by August and September, 4-5 months of the heat and humidity really starts wearing you down.
But if your question is whether it starts to cool off a bit...NO. That doesn't happen until October-November usually. Through September, you can expect heat, high humidity, and daily thunderstorms.
Our strategy for summer visits is hit the parks early and late, go back to the resort for pool/nap time in the middle of the day, and focus on indoor attractions or meals during thunderstorms.
We also start sipping water on the way to the parks and never stop sipping all day. Hydration is very important in high heat and humidity. The summer heat here is not like the heat up north, and heat illness is nothing to play with.