I have been at VB over Labor Day (Sun-Thurs) the last two years in a row. Weather was fine, though last year seemed hotter than the year before. I don't remember any rain, which doesn't mean there wasn't any, only that it didn't interfere with family fun.
Last year the noseeums ate me alive (all in one afternoon) and what I learned is that they are more active at certain temperatures. As a result we made reservations this year for early October, thinking the weather will still be nice and the temperature a bit cooler.
I wouldn't hesitate to go again in September, though, now that I know enough to get insect repellant.
As for hurricane possibilities -- we all know that anything can happen any time.
MJ