We were in WDW yesterday. We didn't go to the party. The rain was some of the worst I've seen in all my visits there. The monorail was down, so we had to Uber back to our hotel to head to the airport. We left around 6pm, and the rain was still heavy. I don't think it lasted too long after that (the heavy stuff stopped around 7 or so), so they probably didn't cancel anything.
Just about every flight at the airport was delayed. Our 9:30pm flight Monday took off at 3:15am this morning. We got to our house around 6am today. Fun times.