Research
MLB temperature and scoring
By OverUnderWeather Research Desk
Cold bats and hot carry are baseball folklore. We matched every dry outdoor game since 2021 to archive temperature at the park across the game window, then measured each game against its own season and its own park — because hot games cluster at warm-weather parks — and compared runs and home runs band by band against mild 70–79°F games.
Study in progress
The temperature aggregates are still compiling. The tables publish here as soon as the first full run completes.
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.
Methodology reviewed by Kerry G. KauffmanB.S. in Statistics, Lehigh University
“After examining the complete methodology and structure of the study, I am in agreement that the Welch’s t-test is the appropriate method when comparing two means.”— Kerry G. Kauffman, 2026-09-26
Cite this research
Free to republish with a visible credit and a link to this page. Ready-made citations below — click to copy.
Frequently asked
Does cold weather actually lower MLB scoring?
Yes, and it is the strongest temperature signal we measured. Games under 50°F score about 1.14 fewer runs than the 70–79°F control after adjusting for season and park (t = −5.08 on 354 games), with home runs down about 0.72 a game (t = −9.25). The effect shrinks steadily as temperature rises through the 50s and 60s.
Does heat boost scoring as much as cold suppresses it?
Not quite. Games at 90°F and above add about 0.64 runs (t = +2.71) and 0.38 home runs (t = +4.32) against the mild control. The 80–89°F band in between adds runs that are not statistically distinguishable from zero (t = +1.60), although home runs are up modestly there. The suppression side is the cleaner, larger signal.
Why adjust for park as well as season?
Because hot games are not spread evenly. They cluster at warm-weather and high-altitude parks like Coors Field and Chase Field, which score differently for reasons that have nothing to do with the thermometer. Every figure here is each game measured against its own season and its own park, so the temperature band — not the park mix — is what moves the number.
Is rain included?
No. The main analysis uses dry games only, so rain is not carrying the temperature result. Rainy games are reported separately as context: 864 games at 9.09 runs and 2.28 home runs, close to the dry-game average of 8.95 and 2.32. We have not measured an independent rain effect on MLB scoring.
Are domes and closed roofs included?
No. Fully enclosed parks are excluded entirely, and retractable-roof parks contribute only games recorded as played with the roof open. There is no temperature to measure when the roof is shut.
Are Over/Under hit rates included?
Not yet. We are backfilling closing totals so the study can report runs-vs-line and Over/Under hit rates. Until that completes we report runs and home runs against the mild control.