How the weather could impact tonight’s MLB Home Run Derby

When you think of a baseball player hitting a home run, there are lots of variables that come into play. Who is the batter? Who is the pitcher? What stadium are they playing at? But what about the weather? 

Wind, rain and snow may come to mind first, but temperature and humidity can influence how far a baseball travels and be a deciding factor in if the ball makes it out of the park.

Warm air is less dense than cold air. Air expands when it’s heated, so the molecules are more spread out. This means there is less air for the ball to travel through, giving it less resistance. 

Now factoring in humidity, warmer air can hold more moisture. Water vapor is light compared to nitrogen and oxygen molecules, so humid air is less dense than dry air at the same temperature.

When it’s hot and humid, the air is lighter, and the baseball can travel further.

A 2023 study claims that “a 1° C increase in the daily high temperature on the day of a baseball game played in a stadium without a dome increases the number of home runs in that game by 1.96%.” A bigger difference in home runs was observed for games played during the early afternoon versus night games because of the larger difference in temperature.

How about cold air? Cold air is more dense than warm air, so the ball has to travel through more air. Molecules move closer together when the air contracts as temperature lowers. 

If it’s cold and dry out, the drier air will have fewer water vapor molecules, so the nitrogen and oxygen comprising the air will be heavier than the humid air would be. 

Ideally, outdoor games in hot and humid climates are most favorable for seeing your favorite team or player hit a home run.

Tonight’s MLB Home Run Derby is in Atlanta, and the forecast calls for no rain and temperatures near 90 degrees with heat index values in the mid-90s. Get ready to watch the ball fly! 

Our team of meteorologists dives deep into the science of weather and breaks down timely weather data and information. To view more weather and climate stories, check out our weather blogs section.