We were just there the 4th though the 13th of January and encountered everything from hats and gloves one morning, to Typhoon lagoon one afternoon (it was chilly in the shade but liveable for a few hours). What I found was that if you planned on being out all day and not back to the hotel was to get a locker, that way you can start out in a jacket, store it when it gets warm, and pick it up again for the evening. Also great was zip off pants for my DD8, he had the best of both worlds. For my DD5, she wore shorts with winter weight tights underneath, she has different ones with Cinderella, Pooh, etc and again, that way she could strip them off as the day warmed up. The weather forecast never seemed to be right while we were down so we just always tried to be ready for everything.