How Weather Affects MLB Scoring: Temperature and Wind in Numbers

Warm air is less dense, so a well-hit ball travels farther. The effect is not subtle. Across more than 11,000 outdoor MLB games from 2021 to 2026, using the temperature MLB records at first pitch:

• Below 55°F: 8.24 runs per game (694 games).
• 55–64°F: 8.30 runs.
• 65–74°F: 8.72 runs.
• 75–84°F: 9.19 runs.
• 85°F and above: 9.79 runs (1,890 games).

That is a gap of about a run and a half between the coldest and hottest games — some of it is the calendar (cold games cluster in April, when pitchers are also freshest), which is why the model estimates the temperature effect alongside everything else rather than reading it straight off this table. In the fitted model, a typical one-standard-deviation swing in first-pitch temperature is worth roughly 4% of a team's expected runs.

Wind

With the wind at 10 mph or more, games where it was blowing out averaged 9.19 runs, cross-winds 8.96 and wind blowing in 8.60. The model turns every forecast into an 'out to center field' component using each park's orientation, so a 15 mph wind straight out counts fully and a cross-wind hardly at all.

Roofs and domes

Domes and closed roofs take weather out of the equation. For retractable roofs the decision is made on the day, so until MLB posts game-day conditions the model assumes the roof is closed when it is colder than 60°F, hotter than 88°F, or rain is likely. Forecasts come from the US National Weather Service; see Data sources.