MLB postseason
MLB Playoff Roof Rules: Who Decides, and What October Weather Does
By OverUnderWeather Research Desk
In October the home team loses control of its own roof. Here is the actual rule, how it has played out in recent postseasons, and what our weather data can and cannot tell you about cold playoff nights.
The short answer
In the postseason the Commissioner or a designee makes all roof decisions, consulting the home club and the umpire crew chief.
Past MLB decisions have used the home club's regular-season criteria: temperature, rain, humidity.
Open vs closed at the same park: about +0.13 runs, within noise (games since 2021).
Open-air games below 50°F: 1.64 HR per game. 85°F and above: 2.76 (regular season).
Playing tonight? Check today's MLB weather and roof status.
The official rule
MLB's ground rules give the home team the call during the regular season. They then add: "During the postseason, the Commissioner or another designated official shall make all decisions regarding roof movement, in consultation with the home club and the umpire crew chief" (MLB.com ground rules).
The same rules say a roof may be moved only once during a game unless weather requires otherwise, and a game that starts open can be closed only for weather reasons.
How it has played out
- Toronto, 2015 ALDS: MLB.com reported that the Commissioner's Office met the Blue Jays and the crew chief before each game, using Toronto's regular-season criteria; the club said about 15°C (57°F) was near the roof's temperature limit (MLB.com).
- Arlington, 2023 ALCS: MLB opened the Globe Life Field roof for a Rangers game for the first time since May 21, citing regular-season guidelines (Sports Illustrated).
- Milwaukee, 2026 NLDS: After a ball struck a roof cable in a closed-roof Game 1, the roof was open for Game 2 (CBS Sports).
Seven parks have retractable roofs. Full list and open-vs-closed scoring: MLB retractable roofs guide.
What late-season data shows
Our games table covers the regular season only, so it holds no playoff games. The closest we can get is the season's final days: 92 open-air games played on October dates (2021–2023), against 1,470 in September.
| Month | Games | Avg temp | Runs | Home runs | Runs vs close |
|---|---|---|---|---|---|
| October | 92 | 68.7°F | 8.28 | 1.91 | +0.39 (89) |
| September | 1,470 | 74.2°F | 8.91 | 2.33 | +0.46 (1464) |
October games had 0.42 fewer home runs (Welch t=-2.93, p=0.004, Cohen's d=-0.25) and 0.63 fewer runs (t=-1.54, p=0.13, not significant). Those October games averaged 68.7°F, so temperature is not the only plausible cause — end-of-season rosters and resting regulars change too. Against the closing total both months finished slightly Over, so we see no betting edge here.
For the temperature effect itself, see how temperature affects baseball; for delays, MLB rain delay rules.
Method and sources
Rules quoted from MLB.com. Game data: regular-season open-air games in our database, 2021–2026, temperature at each park at game time. Written by the OverUnderWeather Research Desk; not independently reviewed.
Where this is applied
These findings feed the game-time read on every MLB venue page, using the same sample-size and significance rules published here.
OverUnderWeather Research Desk
Independent data analysis on public sports and weather records. Studies match historical game outcomes to archived game-window weather, apply pre-set sample and significance rules, and publish null results when that is what the data show. Editorial policy and corrections log.
Cite this research
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Frequently asked
Who decides if the roof is open in the MLB playoffs?
The Commissioner or a designated official. MLB's rules say that during the postseason they make all decisions on roof movement, in consultation with the home club and the umpire crew chief. In the regular season the home team decides.
What criteria does MLB use for postseason roof decisions?
Reporting from past postseasons says MLB applies the same criteria the home club uses in the regular season — temperature, rain and humidity. Each park has its own thresholds, so the same forecast can lead to different decisions at different stadiums.
Can the roof be moved during a game?
Under MLB's ground rules a roof may be moved only once during a game unless inclement weather requires otherwise. A game that starts open can be closed only for weather reasons.
Does a closed roof change scoring?
Not measurably in our data. Across the seven retractable-roof parks since 2021, open-roof games scored about 0.13 more runs than closed-roof games at the same park in the same season — within statistical noise.
Do cold October nights reduce home runs?
Colder air does cut fly-ball carry. In our regular-season data, open-air games below 50°F averaged 1.64 home runs versus 2.76 at 85°F and above. We have no postseason games in the sample, so we cannot measure playoff games specifically.