It's also a note that Fantasmic! has some alterations of cheorgraphy in case of a wet stage. It's the stage manager's decision and can be made at any time, even mid-show. It's essentially the same show, but the jungle animals, snake, and pocahontas actors don't move around as much.
Fantasmic has a alternative show that launches the pryo to an 8 minute musical score should the stage become too unsafe to preform upon.
I have seen shows delayed, but never cancled due to weather. Tinkerbelle's flight is VERY weather specific, wind, lighting, and rain are all taken into account on her flight.