No matter when you go in the summer it’s going to be HOT! But that’s ok - it makes Castaway Cay even more fun. As for crowds - well, the ships carry a set amount of passengers, so you’re never going to exceed that. The ships are huge - you won’t ever feel crowded. I guess the only thing I can say, weather-wise, is that late August hurrican season starts, but ships can alter their courses, so even that’s not too much of a concern.