They start decorating right after Halloween, MK is the first park to be worked on. Usually by the Sunday BEFORE Thanksgiving they have completed all the decorations in the parks and resorts. We always used to go Jersey Week (early November), when we arrived our resort did not have any decorations up, but by the time we left they were just about done. Very cool to see, my DW stayed up all night to watch them erect and decorate the very large tree in WL on one trip !