I took a trip the end of August a few years back, and it was very hot and humid. We definitely got some sunburns--especially the day we went to the water park, when the suntan lotion eventually washed off in the water.
There was one posted by gopherit a while back, I think it's probably in the favorite trip reports thread. I remember reading it because we were going the next August.
When we went last August it was hot, hot, and hot. Just be prepared for the heat and humidity and you'll be fine. And no, none of us got sunburned .