Hi Hope! Jellyfish really come out whenever the water temps are higher. I'm no Vero expert but I know we went to HHI one year in August and it was nearly impossible to get into the water most days because it was so warm and the jellies were everywhere. We had a couple of rainy days to start our week and the first day after it cleared up was OK but then it got really hot and they were everywhere. I would think once the water starts cooling off in the fall you'd be safe. But summer water temps might bring them out.