I go pretty much every year in Dec. In fact, we'll be there the same time as you (Dec 6th-16th). For my Dec trips I seldom ever pack before three days out. I do check accuweather.com daily for several weeks leading up to the trip and do get items out and put them in a spare bedroom. When getting things out I get shorts, tshirts, long sleeve shirts, wind pants, a pair of jeans, a fleece jacket, a thin pair of gloves, a warm hat and scarf, a swim suit, etc. In other words a little bit of everything for any kind of weather. Then about two or three days out I check accuweather.com and pack mainly for what they say the weather will be. However, even if they say the weather is going to be warm, I'll still pack one pair of long pants, a sweatshirt, thin gloves, and a fleece jacket. If they say it's going to be cold, I'll pack mainly cold weather clothes, but will still throw in a swimsuit and a couple pairs of shorts. I've been down there too many times when the weatherman called for cold weather and I burned up or called for warm weather and we froze. Some trips we've worn shorts and swam at the beginning of the trip, but four days later were in pants, long sleeve shirts, light jackets, and gloves and still froze. Dec weather in Orlando is just unpredictable and changes so quickly. I go to WDW 4-6 times a year and usually do carry on only. Only for our Dec-Feb trips do I ever check a bag and it's because we have to carry just a little of each type of clothing to be prepared for any type of weather. I still remember the trip we took the first week of January one year, the weatherman had predicted cold weather all week, so I just packed two pair of shorts and eveyting else was cold weather clothes. It was sooo hot that whole week, I had to wash out those same two pair of shorts every night. The cold weather stuff never got worn. I took my grand daughter back the same week exactly one year later and we almost froze. Dec 2010 it was so cold down there, I again almost froze. I didn't realize Florida could get that cold. However, I went back the exact same week in 2011 and wore shorts all week. You just never can tell and even accuweather.com is frequently wrong, plus as another poster said the weather can go from warm to freezing and back to warm in just a matter of days. More than once we have swam and almost froze on the same trip. This southern girl doesn't swim if it's the least bit cool. I don't do cold weather, so you know the weather really fluctuates if we can comfortably swim and then freeze just a few days later on the same trip. lol