It is very hard to predict. You really will not know until you are there. We were at WDW the first week of December last year, and some nights we had on short sleeve shirts and were still pretty warm....other nights we had to wear coats and were freezing! You need to pack clothes for warm and cold weather. I bought a cute Disney Christmas sweatshirt for my son to wear to the Christmas party....and he could not wear it because it was so warm on the night of our party!