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September 15, 2005

How Weather Affects The Ballpark

Yesterday’s Baseball Prospectus scooped me:

The Rangers can mash, but unless owner Tom Hicks relocates the franchise to Alaska, Texas is going to have to deal with its unique greenhouse effect in developing pitchers--according to research by James Click, the unforgiving summer in Arlington inflates offense in a bell-curve fashion, as runs/game and slugging jump at Ameriquest in the season's middle months.
I was mildly disappointed to read this. About a month ago, I was playing around with the Ranger game results from 2002-2005 and found that The Ballpark’s inflation of offense was pretty mild in the season’s first and last months. Instead of writing an entry immediately, I intended to wait until the season ended so that I’d have more data. Here I was, thinking I’d unearthed a potentially useful bit of information all on my own. Silly me.

Anyway, yes, the Ballpark does tend to inflate offense when the temperature peaks. In April and September, the Ballpark plays as a garden-variety hitter-friendly park. From May through August, it becomes the stadium we know and love (or loathe):

“Raw? Park Factor indicates the simple division of runs at home by runs on the road. Interestingly, the park factors do not correlate especially strongly with the average daily high temperature:

September is slightly warmer than May and much warmer than April but has the lowest park factor. May is the second coolest month but plays as offense-friendly as July and August. I don’t know why. Using only four years of data probably creates some statistical noise, and the monthly composition of Texas opponents and road parks may also play a role in skewing the data.

Posted by Lucas at September 15, 2005 02:05 PM