How Weather Affects MLB Outcomes

Temperature and Ball Carry

Temperature affects baseball outcomes through a simple physical mechanism: warm air is less dense than cold air. Less dense air offers less resistance to a batted ball. The result is that balls travel farther in warm weather than in cold weather, all else being equal.

The Physics of Warm Weather Offense

Research has quantified this effect with reasonable precision. A ball hit in 90-degree weather travels approximately 4-6 feet farther than the same ball hit in 50-degree weather. That difference sounds small, but it turns warning track fly balls into home runs. Over the course of a game with dozens of batted balls, the cumulative effect is measurable.

This is one reason why run scoring tends to be higher in summer months than in April or September. It is not just that pitchers are fresher early in the season or tired late. The physics of ball flight favor offense when it is warm.

Cold Weather Complications

Cold weather creates challenges beyond reduced ball carry. Hitters report that cold weather makes the bat sting more on contact, particularly on pitches off the sweet spot. This discomfort may lead to slightly more tentative swings. Pitchers also report difficulty gripping the ball in cold conditions, which can affect command and breaking ball movement.

Early-season games in northern cities often feature suppressed offense for these reasons. The ball does not travel as far, hitters are less comfortable, and pitchers may have trouble executing their secondary pitches.

Wind Direction and Magnitude

Wind is perhaps the most significant weather variable in baseball. The direction and speed of wind can dramatically alter expected outcomes, particularly at exposed ballparks.

Wind Blowing Out

When wind blows out toward the outfield, fly balls carry farther than normal. Wrigley Field is the classic example. On a day with 15-20 mph winds blowing out to center, the park transforms into a hitter's paradise. Balls that would normally be caught at the warning track sail into the bleachers.

Wind blowing out increases expected run totals and particularly benefits power hitters who generate fly balls. Ground ball hitters and pitchers who induce weak contact are less affected.

Wind Blowing In

The opposite effect occurs when wind blows in from the outfield. Fly balls die at the track. Would-be home runs become lazy outs. Pitchers who generate fly balls benefit enormously. Offense becomes more dependent on line drives and ground balls finding holes.

Strong wind blowing in can suppress run scoring significantly, sometimes by several runs per game compared to calm conditions.

Crosswinds and Unpredictability

Crosswinds create different challenges. They push fly balls left or right, making them harder to track. Outfielders misjudge balls more often. Pop flies become adventures. The effect on run scoring is less predictable than straight in or out winds, but the chaos factor increases.

Which Parks Are Most Affected

Not all ballparks are equally exposed to weather. Wrigley Field in Chicago is famously wind-affected, with conditions that can vary dramatically from one day to the next. Kauffman Stadium in Kansas City, Coors Field in Denver, and Oracle Park in San Francisco are also notably weather-sensitive.

Meanwhile, covered stadiums and those in weather-stable regions see minimal variation. Games in Miami, Arizona, or Texas (in the dome era) are relatively insulated from weather effects.

Humidity and Its Effects

Humidity is widely misunderstood in baseball analysis. Many assume that humid air is heavier and suppresses ball carry. The physics suggests otherwise.

The Humidity Myth

Water vapor is actually lighter than the nitrogen and oxygen molecules that make up most of the atmosphere. Humid air is therefore less dense than dry air at the same temperature and pressure. If humidity had any effect on ball carry, it would actually help the ball travel slightly farther.

In practice, humidity effects are small enough to be essentially negligible compared to temperature and wind. The perception that humid, heavy air suppresses offense is largely a myth that persists despite the physics.

Where Humidity Matters: Pitcher Grip

Humidity does affect pitchers, but not through ball flight. High humidity can make the ball slick and harder to grip. Pitchers who rely on precise spin and movement may struggle in muggy conditions. Sweat and moisture accumulate faster. Control can suffer.

Conversely, very dry conditions can make the ball feel different. Pitchers accustomed to humid climates may find the dry air in Colorado or Arizona affects their feel for certain pitches.

Altitude: The Coors Field Factor

While not strictly weather, altitude is often discussed alongside weather effects. Coors Field in Denver sits at over 5,000 feet elevation, where the thin air has profound effects on baseball.

Reduced Air Resistance

At high altitude, air density is significantly lower. Batted balls travel much farther. Breaking balls break less because there is less air to create movement. Curveballs flatten. Sliders sweep less. The physics fundamentally change the game.

Coors Field consistently ranks as the most offense-friendly park in baseball, and it is not close. The humidor installed to add moisture to baseballs has helped somewhat, but the altitude effect remains substantial.

Implications for Prediction

Any prediction model must account for the Coors effect. Pitching statistics generated at Coors are misleading. Hitting statistics generated there are inflated. Road splits provide a better picture of true talent for Rockies players. Visiting pitchers often struggle in their first exposure to the thin air.

Why Weather Affects Totals More Than Sides

Weather tends to affect total run scoring more predictably than which team wins. Understanding why helps clarify when weather information is most useful.

Symmetrical Effects

Most weather effects apply to both teams equally. Wind blowing out helps both offenses. Cold weather suppresses both offenses. Unless one team is specifically built to exploit certain conditions, weather tends to shift the total runs expected without clearly favoring one side.

A fly ball team facing a ground ball team in wind blowing out might have an advantage, but these asymmetries are smaller than the overall shift in expected scoring. For prediction purposes, weather is more useful for assessing totals than for picking winners.

The Practical Application

When evaluating a game, consider weather effects primarily in the context of run expectation. Will this be a high-scoring or low-scoring game? Extreme wind blowing out at Wrigley points toward higher scoring. Cold, calm conditions at a pitcher-friendly park point toward lower scoring.

For moneyline predictions, weather is a secondary factor unless specific matchups create asymmetric advantages. For run total predictions, weather is often the most important situational variable.

Integrating Weather Into Prediction

A complete prediction approach incorporates weather alongside other factors. The process might work as follows:

First, check the forecast for game time. Note temperature, wind speed, and wind direction. Identify whether conditions favor offense, pitching, or are neutral.

Second, consider the park. Is this a weather-sensitive stadium or one that is largely insulated? Open-air parks in the Midwest and Northeast are most affected. Domes and Southern stadiums are least affected.

Third, adjust expectations accordingly. If strong wind blowing out is expected at a hitter-friendly park, expect elevated scoring. If cold temperatures and wind blowing in are forecast, expect suppressed offense.

Fourth, weight weather appropriately relative to other factors. Starting pitching, bullpen quality, and offensive strength still matter more on most days. Weather is a modifying factor, not the primary driver of outcomes. For the full framework, see How MLB Games Are Predicted.