Disney keeps at least one waterpark open during winter,so they're also open 365 days a year,however I heard on another thread that there have been days that was like in the 20's or low 30's in the morning with an expected high of around 50-55 and they actually close the park,I couldn't tell you for sure since I would never visit a waterpark in that weather.Wet n Wild is also supposed to be open 365 days a year and I do remember driving by it on a very cold day and it was definitely closed,I'm sure Aquatica will have similar operation,It's probably a handful of days in a year that they'll have an issue with weather being too cold.