I have gone many times over Thanksgiving and Christmas and the important thing to do is bring clothes for both extremes. Sometimes, it may be closer to 80 in the day with evenings in the 60s, and others could be closer to 60 during the day and in the 40s at night. I usually try to layer, but I'll usually wear a button with a sweater or light jacket as my layers. You can also buy a themed sweatshirt if needed at the party.