Research
Wind blowing out: does the betting line already know?
Everyone knows wind blowing out adds runs. We tested whether the closing total already accounts for it, using every outdoor MLB game with a line since 2021.
The headline
The market already prices it. Games with wind blowing out at 10+ mph finished no differently against the closing total than every other game.
Wind out 10+ mph games
1,250
avg 13.3 mph
vs other games, runs over close
+0.07
t = 0.53 · noise
Over rate
49.4%
597 Over · 612 Under · 41 push
Key finding in plain English
Wind blowing out adds home runs, but league-wide it barely moves total runs — and whatever it does is already in the closing total. Blindly taking the Over when the wind is blowing out would have won about as often as a coin flip, before the bookmaker's cut. This was the one test we set before looking at the data, and the answer is no edge.
By wind direction and speed
| Wind | Speed (mph) | Games | vs all games | t | Over rate |
|---|---|---|---|---|---|
| Blowing out | 5-9 | 2,148 | +0.12 | 1.29 (noise) | 50.6% |
| Blowing out | 10-14 | 950 | +0.13 | 0.91 (noise) | 50.1% |
| Blowing out | 15+ | 300 | -0.16 | -0.64 (noise) | 47.1% |
| Blowing in | 5-9 | 1,073 | +0.02 | 0.13 (noise) | 49.3% |
| Blowing in | 10-14 | 364 | -0.44 | -2.10 (directional only) | 46.0% |
| Blowing in | 15+ | 78 | -0.39 | -0.91 (noise) | 47.4% |
| Across the field | 5-9 | 2,639 | +0.03 | 0.29 (noise) | 49.1% |
| Across the field | 10-14 | 1,145 | -0.08 | -0.62 (noise) | 48.1% |
| Across the field | 15+ | 326 | 0.00 | -0.01 (noise) | 51.9% |
| Calm (under 5 mph) | under 5 | 2,524 | -0.06 | -0.63 (noise) | 48.7% |
"vs all games" is runs above the closing total in that group minus the +0.45 average across all 11,547 games. Speed-band splits are supporting detail, not pre-set tests, so any band that clears |t| ≥ 1.96 is labelled directional only.
Method
- Outdoor games 2021–2026 with a closing total; roof-closed and dome games excluded.
- Wind is the game-window archive reading, resolved against each park's home-plate-to-center-field bearing into out, in or across; under 5 mph is calm.
- Primary test, set in advance: wind out at 10+ mph vs all other games, runs minus closing total, Welch t-test. Real only at |t| ≥ 1.96.
- 40-game minimum per group. No-effect results are published.
- Closing totals are ESPN's last consensus line, single source.
Related research
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.
Frequently asked
Does wind blowing out mean the Over hits in MLB?
Not against the closing total. In 1,250 outdoor games with wind blowing out at 10+ mph (2021–2026), games finished 0.07 runs closer to the Over than all other games — a gap that is pure noise (t = 0.53). They went Over 597 times and Under 612 times.
Does wind blowing out add runs at all?
It adds home runs (+0.18 per game against calm in our wind direction study) but no measurable total runs league-wide. The exception is a few parks, Wrigley Field above all. This study adds the betting line: even where the wind matters, the closing total already reflects it in the average game.
Why do all groups finish slightly above the closing total?
Across every outdoor game, final runs averaged 0.45 above the closing total, yet more games went Under than Over. A few high-scoring blowouts pull the average up. That is why we compare each wind group with all other games instead of with zero.
What about wind blowing in?
Wind blowing in at 10–14 mph finished 0.44 runs lower against the closing total than the average game (t = -2.10, 364 games, 161 Overs vs 189 Unders). It was not a test we set in advance and it sits among ten speed bands, so treat it as directional only, not a proven edge. At 15+ mph blowing in, there were only 78 games and no clear gap.