MLB totals and weather
Wind, temperature, and ballpark shape determine MLB run-scoring. The weather inputs that move totals and the ones that retail markets underprice.
Baseball is unusually weather-sensitive. Wind speed and direction, temperature, and humidity all affect run-scoring. Books price these inputs into MLB totals; the market often underweights game-day specifics versus the season-average baseline.
Wind
Wind is the largest weather variable in MLB total pricing. Direction matters more than speed. A 15 mph wind blowing out adds approximately 0.5 to 1.0 runs to the expected total at parks with prevailing wind effects (Wrigley Field is the canonical example). The same wind blowing in can suppress totals by similar amounts.
| Wind condition | Total adjustment |
|---|---|
| Calm or under 5 mph | Baseline |
| 10 to 15 mph blowing out | +0.4 to +0.8 runs |
| 20+ mph blowing out | +0.8 to +1.5 runs |
| 10 to 15 mph blowing in | -0.4 to -0.8 runs |
| 20+ mph blowing in | -0.8 to -1.3 runs |
| Cross-wind | Smaller effect, sometimes adds variance |
The book bakes expected wind into the line. The bettor's edge comes from game-day forecasts that update faster than the line moves, particularly for afternoon games where wind tends to pick up later in the day.
Temperature
Hot weather adds runs, cold weather suppresses them. The mechanism is air density: warmer air is less dense, the ball travels farther, more fly balls become extra-base hits. Effects are modest but consistent.
RULE OF THUMB
every 10F above 70F → +0.10 to +0.20 runs
every 10F below 70F → -0.10 to -0.20 runs
90F game vs 60F game
expected total runs ~ 0.6 runs higher at 90F
line should already incorporate this
edge comes from forecast surprisesHumidity matters too, but its effects are smaller and harder to model. Some sharp bettors weight humidity in the same direction as temperature; the public usually ignores it.
Rain delays and rainouts
MLB games go to a result if 5 innings have been played (4.5 if the home team is leading). A rain delay does not void a bet. A rainout postpones the game; what happens to your bet depends on the book and the timing of the rescheduled game.
If the game is moved to a later date, most books void the bet (you get your stake back). If the game is moved to a doubleheader the same day, the bet usually stands and is settled when the game goes final. Read the book's MLB rules. They differ.
Ballpark factors
Ballparks differ in size, geometry, altitude, and roof status. The most well-known is Coors Field (Denver), which inflates run scoring by 25 to 35% relative to a neutral park because of altitude. Yankee Stadium has the short right-field porch that helps left-handed pull hitters. Petco Park (San Diego) historically suppresses scoring.
| Park | Run environment |
|---|---|
| Coors Field (DEN) | +25 to +35% (altitude) |
| Great American Ball Park (CIN) | +5 to +15% (small dimensions) |
| Yankee Stadium (NYY) | neutral overall, lefty-friendly |
| Tropicana Field (TBR) | -5 to -10% (dome, dimensions) |
| Oracle Park (SFG) | -10 to -15% (deep right-center) |
| Petco Park (SDP) | -5 to -10% |
Books price park factors into the baseline total. The edge from park factors is in noticing how a park interacts with that day's specific weather (a windy day at Wrigley behaves very differently from a calm day; a hot afternoon at Oracle plays larger than a cool evening).
Game-time updates that move totals
- Lineup changes. A star bat scratched late drops the total.
- Bullpen availability. Confirmation that a closer is unavailable today affects late-game scoring expectations.
- Wind shift confirmation. Forecast wind speed updates within hours of first pitch.
- Umpire assignments. Some plate umpires call a notably larger or smaller strike zone, affecting scoring meaningfully on the margins.
What to read next
MLB run lines covers the side market. MLB pitching matchups covers the dominant pricing input on every MLB game.