We were there at Christmas 2 years ago. It was sunny and hot at Aulani everyday, but it was rainy and miserable everywhere else (Waikiki, North Shore, etc.). Reminded me of how Kona is sunny everyday but could be rainy just a few miles away. Definitely warm enough to go into the ocean. There wasn't a big Christmas'y feel there (on the entire island, for that matter), in case you're expecting that. A few trees here and there scattered throughout the resort, garland. Not much else. When we were there, it was really new, and we didn't take note of any Christmas activities. May be different now that it's been open longer.