Hi,
I have been twice, both holidays were in September... 2004 and 2005. The weather for both was fine (we were also aprehensive after reading we had chosen to go in hurricane season!). It was neither too hot, nor too cold, shorts and t-shirts/vests were fine.
However, we did have a hurricane on the second holiday and I think this is one and the same as mentioned in a post above. It lasted overnight (extremely wet and windy) but didnt cause us any major problems. We were due to go home a few days later but we just went to WalMart and got ourselves some supplies - water, candles, bread, milk etc just to keep us going really... oh and books/puzzles to keep us occupied in case the electric was lost (which it wasnt). If you are worried there is always someone you can contact about what to get or do etc.
We've just booked to go again this year... this time in October so hopefully the weather will still be fine