I've gone the first or second week of December the past 6 years. Three of the years it was perfect (98, 99, 01) - highs in the high 70's/low 80's, nights just a little cool. 2000 was cold, highs only in the low 60's and down into the 40's in the evening. 2002 & 2003 were a mixed bag. 2002 had a lot of rain, twice we had 24 hours + of straight rain.
On the day we arrived last year, the high was only in the low 50's! We went to see Wishes that night and I was so cold, I had on a flannel lined denim jacket and gloves, sweater and jeans. It warmed up after that, we had some days in the 70's. Watch the forecast and bring a light winter coat and gloves if the high temps are 60's or below. My Mom laughed at me when I brought gloves in 2000, guess who bought a pair there? They bring them out at the cash registers when it's cold, just like the ponchos when it rains. I noticed they were selling alot of santa hats last year.