Depends where you bought it from. If you bought it on Ticketmaster then you go to the rescheduled game. If you bought it on StubHub then call the customer service line, if the game is canceled due to rain StubHub will credit your StubHub account to use towards another event. That's why I always use StubHub and not Ticketmaster. I never but tickets anymore until I know the weather forecast.
The understanding is that if a game is cancelled beforehand, you should receive a full refund. However, if the game begins and is suspended for rain and then discontinued after a certain number of innings, you may be out of luck.
You can exchange it at Ticketmaster for a future game.
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