Like everyone has said, you just kind of have to be prepared for anything (Which stinks for packing, I know!). We have been there the last 3 Decembers. We have been able to go into the pools each trip, we have also been in sweatshirts and jeans all three trips. I remember two years ago we were all in tank tops and shorts and sweating in the MK one day, and the next we were all freezing and had to buy clothes in HS. This year we are going in January, so I'm guessing we won't have as much warmth as we have experienced in Dec., but I will still probably pack a few capri length pants/t-shirts, as well as heavier things.