Weather plays a defining role in shaping the behavior of the air, and by extension, how a ball travels through it. While the physics of drag and spin are universal, the environment in which they act is anything but. This article unpacks how temperature, humidity, pressure, and altitude work individually and together to influence air density and the resulting ball flight in sports.
Atmospheric conditions don’t just shape the field… they shape the physics.
Temperature
One of the most commonly referenced weather-stats we hear, from the great work of Dr. Alan Nathan, is that an increase in 10°F can add approximately 3 feet of distance to a fly ball.
Higher Temperatures = Lower Air Density
There is less drag (air resistance) in warmer air, because the air molecules are more spread out; reducing air density and “boosting” ball flight distances. While warmer temperatures don’t make fastballs faster, pitches will better retain their velocity from the initial release, resulting in a higher velocity at the plate when compared to colder conditions (all other things equal). Respected golf instructor Andrew Rice found with TrackMan data that when temperatures rise about 10°F from morning to afternoon (which happens on most days) the ball carries roughly 2 yards farther.
Humidity
While you may often hear wet, humid weather described as “heavy”, counterintuitively, humid air is less dense than dry air. This is because water vapor molecules actually weigh less than the oxygen or nitrogen molecules they replace. The impact, however, is relatively small.
Higher Humidity = Lower Air Density
In coastal regions, dense marine layers can further complicate things by layering cool, humid air near the surface and subtly altering both air density and ball behavior in ways that aren’t always intuitive.
Moisture in the Mix
In sports like tennis and baseball, the balls themselves can absorb moisture from humid environments, making them heavier and altering their aerodynamics and their response to impact. This can have a significantly greater impact on ball flight compared to humidity’s influence on air density and drag. In contrast, golf balls are built with impermeable covers, preventing significant moisture absorption and maintaining consistent behavior regardless of humidity.
Recognizing how important this is, Major League Baseball now requires all teams to store baseballs in humidors, ensuring that moisture content, and therefore ball performance, emains consistent across different parks.
Atmospheric Pressure and Altitude
Altitude is one of the most recognized factors in sports performance because of its large impact. The effect comes mainly from the drop in atmospheric pressure that occurs with elevation which lowers air density. Atmospheric pressure itself is shaped by both altitude (the amount of atmosphere above you) and, to a smaller extent, large-scale weather systems. Low-pressure environments reduce air density, while high-pressure systems increase it.
In Denver, at roughly one mile above sea level, air density drops to about 82% of sea-level conditions. According to Titleist, this results in approximately a 6% increase in distance with your driver. At Coors Field, fly balls travel 5–10% farther and pitches show less movement due to Magnus effects, leading to increased home run totals. To try and counteract this effect, Coors Field has some of the furthest fences of any MLB park!
Higher Altitude = Lower Air Density
Atmospheric pressure changes independent of altitude are usually gradual and relatively small compared to the dramatic drop caused by increasing elevation. However, shifts between low- and high-pressure zones can still influence weather conditions, with low-pressure systems bringing rising air, clouds, and instability, and high-pressure systems leading to sinking air, clear skies, and more stable conditions.
Lower Atmospheric Pressure = Lower Air Density
Sport-Specific (Ball) Considerations
In golf, atmospheric pressure impacts the ball’s flight through changes in air density but does not alter the ball’s internal pressure, since golf balls are solid and sealed.
In other sports like football, however, external atmospheric pressure can affect the internal pressure of the ball itself, which is why the NFL strictly regulates football inflation between 12.5 and 13.5 psi, a standard that became widely known during the “Deflategate” controversy.
In tennis, ball pressure is not actively regulated during matches, meaning that external pressure and altitude can cause noticeable differences in ball behavior. To address this, the International Tennis Federation (ITF) mandates the use of special high-altitude balls at tournaments held above 4,000 feet.
These pressure differences have minimal impact once a ball is in flight, but can significantly affect how the ball compresses and rebounds, influencing bounce, “feel,” and energy transfer when struck or contacting a surface.
How Atmosphere Alters Outcomes
Weather’s influence on air density provides a scientifically grounded explanation for why the same swing, serve, or throw might produce vastly different outcomes in different conditions. These environmental factors don’t just change the feel of the game, they change the physics, and in doing so, influence decisions made by players, coaches, analysts, broadcasters, and even fans.
Key Takeaways:
- Higher temperatures lower air density, allowing balls to travel farther and better retain speed.
- Humidity reduces air density slightly, but can affect ball mass and elasticity depending on the sport.
- Higher altitudes and lower pressures significantly decrease air density, increasing carry distance and reducing movement on pitched or spinning balls.
- Sport-specific equipment can respond differently to changes in atmospheric variables, with many professional sports organizations having introduced regulations to manage.
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