Johnson: The wondrous and withering baseball weather

From Brad Johnson with SABR member Daren Willman at The Hardball Times on April 11, 2014:

At The Hardball Times, we spend a lot of time quantifying different events that occur on the baseball field. We don’t do this just because we can, but because we want to understand where value is created and lost. One of the areas where we don’t do a great job is with weather.

As somebody who played through college, I consider weather to be one of the three strongest influences on performance. I’ve played baseball in rain, snow, sub-freezing temperatures, oppressive humidity, and skin-melting heat. On occasion, those less than ideal conditions were combined (especially heat and humidity). When the field was wet, I regularly made wild throws. As a pitcher, my velocity would drop as much as 10 mph from its peak in cold conditions. Professionals obviously have many advantages, from climate controlled clubhouses to new baseballs for every pitch if needed. But if weather affects amateurs, then it follows that it probably affects professionals.

Not much work has been done to discover how weather affects the outcome of major league games. I’ve teamed up with data specialist Daren Willman — who runs the indispensable Baseball Savant website (and two others as well) — to further explore the relationship between weather and game outcomes. Daren developed an excellent tool for visualizing temperature by date. Our sample — derived through the power of Retrosheet — covers 1980-2013, and breaks down every game for each team by start temperature. You’ll notice that before 1997, there are gaps in the data. You’re not reading it wrong — the data from 1980-1996 is simply incomplete. Overall, the sample is 59,438 games played with documented weather data. Included in the data set are the teams that played, score, start time, game length, temperature, field condition, wind speed/direction, precipitation, and attendance. In many cases, the field condition, wind direction, and precipitation are unknown.

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Originally published: April 11, 2014. Last Updated: April 11, 2014.