we went on the first week of december in 2016 and the weather was dry and sunny for the 5 days but it was pretty cold, especially queuing for almost 3 hours to get into Santas Grotto!
Crowd wise i thought it was busier than i was expecting, ive later found out that there are some Spanish bank holidays around the 6th-9th and a lot of Spaniards travel to disney.
And i also noticed that a lot of the counter restaurants start closing around 4pm so the queues to get a warm drink are quite long in the remaining outlets open.
but its at night when christmas comes alive at disney. The lights are amazing. and the huge christmas tree all lit up. magnifique!!
and ice skating outside the hotel new york at night was wonderful.