If a game doesn’t start on time, the bet will remain in the queue and be considered active after the first pitch. In the event that the weather causes a push to the next day, the bet can remain active barring any other changes to the circumstances, but the sportsbook can also void it at its discretion. For delays after the game is underway, bets will remain active as long as the game is expected to be completed the same or next day. There may be some other quirks here and there, so be sure to consult the house rules for MLB at the books you are playing for full details on how they handle weather-related issues.