Weather...hot and very humid. Prone to hurricanes at that time..and thunderstorms that are truly incredible. Crowds...not so bad. If low crowds are what you're looking for, this isn't a bad time to go.
We have been about that time frame the past two summers. In '03 it was hot/humid but nothing we couldn't take. We did have some pretty intense thunderstorms with torrential rain but that was only a day or two and happens mid afternoon into early evening. Last year we all know what happened. We checked in the same day H. Charley did. The humidity after that was not to be believed. We were spent by about 6 each night.
Would we go again at this time of year? I think so. We're going in mid-June and it will be hot/humid/crowded then too!!!