We were on the 4 night Wonder last summer, late June. It spritzed on us during the sail away. It poured during the Nassau deck party and had to be moved indoors. There was a thunderstorm way off in the distance later in the day at Castaway Cay (which was pretty neat to watch from Serenity Bay).
On our at sea day, the captain kept steering the ship away from storms. In fact as the sun was rising, I went out onto the verandah and watched the ship turn away from a storm with a rainbow coming out of it...Just gorgeous!
It was very hot, but that's okay!