We just returned from a cruise that included a Cay visit. Weather was in the low sixties with wind gusts to 40mph. They had to shut down umbrellas and the wind literally blew 2 people out in the water so far they had to go get them - but I will tell you, even in those conditions, people loved the water. My family members rented bikes, and went snorkling; I heard no complaints from them. As for myself, I am from upstate NY, so I thought the weather was wonderful and the water warm. I think it depends on the individual, but the suggestions from the previous writer are good ones. Don't miss the chance to visit the Cay, despite the weather. Castaway Cay is beautiful.