A rain delay in baseball is when a game is delayed or canceled due to inclement weather. Baseball is a sport that needs clear conditions. A wet field can be dangerous for players to run on and make gameplay difficult. A delay can be called before a game with the start time pushed back or during the game with an indeterminate break in play.
In Major League Baseball, there is no set wait time for wait delays. Furthermore, rain delays have many nicknames both in and out of baseball and around the world. Common nicknames for rain delays include "rainout," "washout," and "rain stopped delay."
Six teams in Major League Baseball teams currently have with retractable roofs in their home parks: Toronto Blue Jays' Rogers Centre, Arizona Diamondbacks' Chase Field, Seattle Mariners's Safeco Field, Milwaukee Brewers' Miller Park, Houston Astros' Minute Maid Park, and Miami Marlins' Marlins Park. Furthermore, Tampa Bay Rays' Tropicana Field has a fixed roof.
It's the umpire's decision whether or not to proceed with the game as they determine if the conditions are safe or not for the players. Many umpires will allow games to continue through light rain. The home team has some input as well, as it affects the fans coming to their baseball arena.
If the weather clears up, gameplay continues. If the rain persists during a rain delay, a game may end up being canceled, teams and fans go home. If this happens, then fans and attendees can use their current tickets or some kind of voucher as a rain check. A rain check is used to admit someone to the baseball park at a later date for no additional cost.
Many people refer to a rain delay and a thunderstorm delay as two separate things while other people use the terms interchangeably. Typically, a rain delay will only occur if it is near a downpour on the field. If it is light rain, the game usually continues as regularly scheduled. However, if there is thunder, the game is more likely to be delayed. This is typically a thunderstorm delay as thunder implies that a heavy storm, as well as lightning, will occur.
The same is to be said for lightning delays. There could be no rain whatsoever, but if there is lightning, a lightning delay is almost certainly going to be called to ensure the players' safety.
In regards to rain delays, thunderstorm delays, and lightning delays, lightning delays are typically taken more seriously as they yield the highest risk to players.
There are a few other weather-related delays that are less common but still occur throughout the season. Fog delays are a common annoyance for baseball players and fans since most of the conditions are favorable but there is low visibility. Fog delays can last for quite some time and are usually less predictable than rain delays.
Towards the beginning of the season, or end of the postseason depending on where the team is located, snow delays can happen as well. These are usually rescheduled if it is ongoing rather than waited out like many rain delays are.