Home runs and pond hockey: a meteorologist explains humidity and sports

BOSTON — The dew point reached record high levels for the date Wednesday in Boston … touching 72 degrees.

What does that mean?

Well it means it feels tropical for late September and downright uncomfortable for some. You probably also noticed condensation on doors and windows across the area, giving us a good idea what we were about to walk into when we stepped outside.

Did you know high dew points and high humidity can have an impact on sports too? Believe it or not… it’s a good thing for the Red Sox playing today at Fenway Park, while the Bruins host a preseason game at TD Garden, it could cause trouble.

The good
Humidity measures the percentage of water vapor in the air. At times you step outside and the air feels heavy… we often think of humidity as something added to the air on a hot and muggy day.

However, for every water molecule that is added to the air, we get rid of a heavier nitrogen or oxygen molecule. This makes the air less dense.

So, in baseball, a ball will go farther on a humid day than it will on a dry day since the air is ‘lighter’ and easier to travel through.

Let’s enjoy the Red Sox hit it out of the park today and partially thank the high humidity (OK… and the players too).

The Bad
Humidity is a huge concern for hockey… even indoors. Most arenas can control the indoor environment to have a targeted humidity at game time of 30-40%, but if the outdoor humidity is above that, the air flowing inside the building can impact the ice.

This typically happens when thousands of fans enter and the doors open. With too much humidity, the shavings on the ice absorb the water from the atmosphere, making the ice heavy and creating more snow.

This leads to a slower ice as the puck will not travel as fast. We also look at the dew point… which is the temperature that moisture in the air will condense out of the air onto any surface that is cooler than the dew point level. Basically, if any structure, like boards or beams in the arena are colder than the dew point, condensation can form causing problems such as drips and moisture damage on the ice.

This condensation is just like the drips that form on a cold glass on a hot summer day… or just like today! Fog formation can also be an issue with a high dew point level near the ice surface.

While the humidity will remain high today, expect a drop and return to drier weather tomorrow.

Cox Media Group