We went last August. Unfortunately, within ten minutes of the party starting, rain and thunder swept in. I live in S. FL, so I am quite familiar with bad weather. But this was not a quick storm. We all had to take shelter in the gift shop for well over an hour until they finally called off the party. It was a mess.
Disney automatically issued a free water park day in everyone's
MDE account. However, I did not deem this sufficient since the party costs more than a one-day visit. I had to visit Guest Services the next day to get a full refund.
I have to say I would hesitate to ever do an After Hours event at a Disney water park during the summer/rainy months. It was miserable being stuck in a gift shop elbow-to-elbow with others as we awaited news. The rain and thunder were intense, so it was not safe to simply leave.
Disney also needs to do better with providing shelter spaces for people during thunderstorms. It was a nightmare trying to catch a bus back to the resort in that weather. We were all stuck standing under trees in the parking lot, the one place you are always told
not to be during an electrical storm.
*They do not cancel for rain. So do not expect a refund for rain. They only cancel if there is thunder for a certain amount of time (who knows what that is).