The answer is variable! I have spoken to people who have had good weather but we were there in the middle of last December and whilst we had one or two warm days, we also had very chilly days and really cold evenings.
We knew it is inclined to be unpredictable in December and so took jumpers and coats and we certainly needed them most evenings (particularly for sitting and watching the outdoor evening shows such as the Candlelight Processional and Fantasmic etc.)! I did not wear shorts once but took them just in case!
We were in Orlando Dec 26th 2000 for 11 nights. We were not prepared for the very cold weather. 5 or 6 nights we had frost on the car overnight with an average of only around 13oC thru the day.
Had some friends go last Dec started in Orlando then down to Keys said it was warmer further down you went. check out website below gives you history of weather on every day you want.
History & Almanac http://www.wunderground.com/US/FL/Orlando.html
Wayne
Hope it is warmer this year will be there Xmas Day to New Years Day.
We were there the week before Christmas in 2001 and we were very lucky with the weather - mid 80s from memory. BUT, it did get cooler in the evenings - not freezing, just cooler. I've just looked at the photos of us at MVMCP and we're all wearing jeans and sweatshirts/long sleeved tops.
We went over in the fist week of December 1999 to choose furniture for our house.
I vividly remember going to the cinema in Celebration at about 8:00pm in shorts and tee shirt. The locals were all wrapped up in coats and big jumpers complaining how cold it was.
I must admit I was a bit cold in the cinema but that was the air-con!!! It was pleasantly warm outside, though.
We went over Christmas in 1997 and it was freezing. we all wore about 6 layers and were still cold, it was about 35o F which is not much about freezing . Then after 10 days, the temp rose so much that even at night we were in shorts! The answer is pack for every type of weather!