When you plan an outdoor event, you should set a rain date, an alternate day your guests can plan for in case the weather is terrible on the original day.
If you buy tickets to a baseball game which is canceled because of thunderstorms, there will almost certainly be a rain date, an alternative date for the teams to meet up and play ball while you watch from the stands. Your neighborhood barbecue may also have a rain date, just in case it rains this weekend. In fact, some invitations specify something like "rain date next Saturday!"