What should the organizer anticipate, and what should visitors be prepared for—even if it doesn’t happen at all, or happens at a completely different time than anyone expected?
Rain. Or maybe a downpour. Or, worst of all, a thunderstorm with torrential rain.
Last year, we experienced a bit of everything. Fortunately, the storm passed before the program began, but rain either accompanied us or threatened to fall quite often.
The program is always flexible, the organizing team is quick on their feet, and fortunately, you, the audience, aren’t made of sugar. 
Safety always comes first, but the show must go on!