My husband works with weather satellites and is always informing me that the weather forcast is truly only good for 24 hours (maybe 48). We were just there and before we left they were forecasting rain for most of the 10 day trip YUCK! So, I packed everything imaginable, from shorts to coats! Well, the first night or so it was cool.....but no need for a coat....the last day it was so hot and humid I had to go back to the resort and just cool off in the pool! BTW, it never truly rained until one evening at 8 p.m. and it was gone by morning! The point, just be prepared and know that whatever the weather, it is still the most magical place on earth and your going to have a blast! 
