Start checking the local (Anaheim) weather report the week before your trip dates (e.g. abc7.com). Also be checking this board for threads on any weird weather in the parks. For example, over Thanksgiving last year, a serious winter storm came through. It was forecast over a week ahead of time on all the major news outlets. There were several threads going on this board with updates and tips on how to deal with the storm (it was major!) and how to dress appropriately for all day in the parks in severe weather. Arriving DISers knew what to expect and how to prepare because of those threads! Other than that, as pp have said, layers will be your friend. If you will be seeing any nighttime entertainment (e.g. F! and WOC), bring warmer clothes for that. It can get surprisingly chilly in the viewing areas while you wait by the water at night. If your luggage has room, bring at least 2 pairs of shoes so that you can switch off. Some people switch each day (during the mid-day break), others switch every other day. This will help prevent pressure points and blisters. Bring good supportive, moisture wicking socks, too!