I went mid Feb this year. It was great, but you do need to pack twice as much as most other times!
We started out many mornings in coats and gloves--not ski parkas, but good jackets. By mid day we were in shirt sleeves--some days short sleeves, some days long sleeves. Some in our group were happy to leave sweatshirts on all day. (darn skinny people with no body fat to keep them warm! ) By late afternoon when the sun was going down the jackets would come back out. Long pants every day.
We didn't go to water parks, and only swam once in the middle of the day. I chose not to go on Kali River Rapids because I didn't want to be wet and cold, but the rest of my group of adults and kids did (I am a whimp!)
It was actually kind of funny because in the mornings the Lifeguards were patrolling the pool in long pants, coats, gloves and ski caps!!! And there were people swimming in the pool!
I am not a "heat" person, so I really liked this time of year, but I also had a stroller to keep the coats and gloves on when we didn't need them. Not sure I would want to lug them around all day.
Does this help any?