Author: Patrick Kelley (McCormick ’19)

The Temperature

The 2017 MLB season is only a week away, and the reigning champs – Chicago Cubs – are projected to run through the NL Central again. Their home, Wrigley Field, is one of the most storied sports venues in the world. Its ivy walls, bleacher seats, rooftop venues, and overall traditional allure make one of the most popular tourist destinations in the city of Chicago.

Another interesting aspect of Wrigley Field, is the role the weather plays in determining the outcome of a game. Prior to every broadcast, the announcers will inform the fans on the wind situation, as well as the game temperature. During the first week of May in 2016, with the Washington Nationals in town, the game temperature went from 47° for game one, to 73° for game two, and back down to 51° for game three. Three days, three temperatures separated by over 20°. In addition, during this same series, the wind blew out during games one and three, while it blew in during game two at 23 mph. The high variance in weather certainly affects each game differently. In this article, we will look at how game temperatures and wind affect offensive output from both teams.

I analyzed 1,376 games at Wrigley Field since 2000, and found the following data regarding the Cubs offensive output during various game within different temperature ranges:

The median temperature at first pitch of a game at Wrigley Field during this time was 71° Fahrenheit. It is easier to discover the real impact game temperature has when compared to the average game during this time span (all numbers are percentage differences from the average):

Clearly, the Cubs perform better offensively when the temperatures rise. In fact, the Cubs hit nearly twice as many home runs in games played when the temperature is greater than 81° as opposed to when the temperature is below 50°. In addition, the team scores nearly a full run per game more when the temperature is in the highest range than they do when the temperature is in the lowest range.

The Wind

While temperatures certainly contribute to changes in offensive output, many argue that the wind is even more important. At Wrigley Field, wind speed and direction is everything. Since 2000, the distribution of wind directions is as follows:

*y-values are percentages

We can see that the wind blows in almost twice as often as it blows out:

When the wind blows out, the Cubs score 1.7 more runs per game as opposed to when the wind is blowing in at a high rate. They hit almost exactly a full home run per game more when the wind blows out and have a batting average that is 37 points higher. The following chart compares these two data sets to the average cubs offensive output (all numbers are percentage differences from the average output):

We see that the numbers are drastically different from the average.

Final conclusion: wind makes a huge difference in terms of how many runs will be scored at Wrigley Field.

Baseball Reference