Yes, mid August should be less crowded than June/July, but it will probably feel a bit hotter (more humid) and you could end up with a lot of rain ( but no way to know for sure). We've gone in Augs tons of times and wouldn't hesitate to go back.What is your experience traveling to Florida in August? I am hoping to make a mother/daughter trip work sometime next year and I'm currently looking at August. Everything in my is screaming that will be way too hot! However, that may be the best time for us to go. I might can arrange for another time over the summer but would any summer trip really matter? What about crowds, would mid August possibly have lighter crowds?
My ideal time is first 2 weeks of May and/or first week of September, but we'd certainly go back in Aug. if necessary. It will definitely be hot, sticky, humid and probably pretty wet at times.
It takes patience, planning, and plenty of water and AC breaks but we've found it pretty manageable most of the time. If it's the choice between hot Disney or no Disney, or hot Disney or super crowded Disney, we pick hot Disney.