A rainout is a game which is either cancelled, postponed or suspended because of weather conditions. Rainouts are not necessarily caused by rain: snow, fog, flooding, high winds, lightning storms, or other conditions that create a danger for those playing the game or for spectators, can cause a rainout.
If the rain or other condition occurs before the scheduled start of the game, it may delay its start (a rain delay) or cancel the game for that day. The game is then normally rescheduled to be played at a later date, either as part of a doubleheader or when the two scheduled teams have a common open date on their schedules. If the rainout occurs towards the end of the season and the game has no bearing on the championship, it may simply be dropped from the schedule.
Spectators who have bought tickets for a game which becomes a rainout are issued a "rain check" (usually, the ticket stub is considered the rain check). This can usually be exchanged for a ticket for the make-up date, or for another game later that season.
A rainout can also occur after the game has started; at this point the game is "called". If conditions, improve, the game is resumed as soon as conditions permit and played until its conclusion; this is also called a rain delay. If the game cannot be resumed, the following rules apply:
- A game is considered to be a regulation game (also called an "official game") if 4½ innings have been played and the home team is leading, or if 5 innings have been played. If a rainout prevents the completion of a game that has become a regulation game, the result stands, and the remaining portion of the game is not played.
- If the game is not yet a regulation game, it is considered not to have started; all statistics are wiped out and the game is replayed in its entirety.
- If the game is a regulation game but the score is tied when called, or if the visiting team has taken the lead in its last-half inning at bat and the home team has not had a chance to complete its own turn at bat, the game is a suspended game and is resumed at a later date.
- If a suspended game cannot be resumed because of the end of the season, the result is allowed to stand, either as a tie or as a win for the visiting team.