How does the weather affect baseball?

Being a part of WXedge has been an awesome experience. I have learned a lot, and met some great people. I have found that many of us share another common interest (other than weather)-baseball. The twitter conversations about this team and that team, this manager and that player, have been fun. All of this got me thinking about the relationship between our two passions. There are articles on the site about surviving the weather variations at baseball games (I wrote one of them). But what type of effect does the weather have on the game on the field, the actual outcome? I discovered some interesting facts.

Baseball fans know that Coors Field in Colorado is a notorious home-run hitter’s paradise. The ball seems to fly out of there. There’s a logical explanation for that (not poor pitching). Coors Field is high above sea level, and the thinner air promotes greater flight of the baseball. In fact, for every 1,000 feet above sea level, resistance on a moving object is 3% less. So, in the mile-high city of Denver, resistance is about 15% less than at a sea-level park. That means that a ball will travel roughly 15% farther at Coors Field than it would at Fenway, which is close to sea level. It’s good to be a Colorado Rockie, unless you’re a Rockie pitcher. This makes sense, right? 

Let’s a closer look at weather and baseball. So many games are played on hot, humid days and nights. Sometimes, the air is so thick, you can almost cut it with a knife. This must have an adverse effect on the flight of a baseball. Or does it? Interestingly, as humidity increases, air density decreases. In damp air, the large, heavy oxygen and nitrogen molecules are replaced by lighter water molecules, resulting in less density-in essence, “lighter air”. So you might think that a ball would go farther on a dry day than on a humid day. But for every water molecule that is added to the air, a heavier nitrogen or oxygen molecule is removed. Since the addition of humidity actually makes the air less dense, a ball will go farther on a humid day than it will on a dry day. For example, when 10% of air molecules are replaced by water molecules (a humid environment), a ball that would travel 400 feet in dry air will travel approximately 419 feet. This could mean the difference between an out and a home run, or a win and a loss. This may leave fans lamenting, “if only it were humid. That ball would have gone out and my team would have won!”

Humidity can affect pitching, too. A curve ball curves because as the ball slows on its journey from the pitcher’s hand to the plate, the spin on the ball takes over, and causes the ball to curve (or sink). If there’s more resistance in the air, the ball will curve less. So you could make the argument that drier conditions adversely affect pitchers. But as we saw above, dry conditions also adversely hitters, so at least there’s some fairness in that.

In any event, baseball season is in full swing. I hope everyone has the chance to get to a game this summer. When you’re there, just remember, if it’s humid, you may see a few more home runs.

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