Just know that the rain has the potential to cancel parades/shows/outdoor meet and greets, etc…. It doesn’t have to be a thunderstorm.
Exactly this!
The parade will initially be postponed, so you may be left waiting to see if it goes or not, taking additional time during your evening.
Shows will get cancelled if there is
any rain, same with outdoor meet and greets.
Fireworks will go off, but they will wait for the best moment, and it will not be on a schedule . Say they are scheduled for 10:15; they may send them off at 10:47 or 10:54 or 11:03 or really, anytime, and you will only hear the announcement immediately before, so it is difficult to determine whether to wait or try to do something else. We've waited for 30 minutes past their scheduled time, only to make the decision to get on Space Mountain, made that line, and come out of it to see that the fireworks were ending.
It's not the rain per se, but the disruption. It's not quite fair to say "put on a poncho and enjoy" since many of the aspects that guests are there for are cancelled.
We don't have a good record with weather and the parties, so we have not gone to them in a few years. They sell out more than a week in advance, and you have to take a leap of faith that the weather will be good before you have a reliable forecast.
If it's 7pm, and raining and the forecast looks terrible, you can go to Guest Relations, and very likely, they will exchange your party ticket into something like a 1-day base ticket that you can use in the future.