Home Runs and Cold Weather

If you read the post immediately previous to this one (and having seen my site hit counts, that's a REALLY BIG if), you'll have read that the White Sox hit four home runs in their 5-2 victory over the Royals. In the post-game discussion, Chicago sports radio hosts Dan Bernstein and Terry Boers wondered whether there was a difference in the number of home runs in cold weather vs. warm. I'm sure this has been studied before, but the raw data isn't easy to come by. To contrast, if I were so inclined, I could see how NFL teams perform by weather conditions using tools available on pro-football-reference.com (and completely debunk the silly notion of "Bears Weather"), but baseball-reference doesn't have that option. Therefore we have to use something else.

It's also not a simple matter of looking at splits at baseball-reference. Everything we need is there, but not discretely broken out so that we can see how many home runs were hit at Wrigley Field vs. some other park in a given month. Luckily, I have play-by-play data from 2009-2012 that allows us to make those distinctions. This first table is the average hits per game with the MLB teams broken down by the three following categories:

I don't really know the correct way to categorize the retractable domes, since I'm not sure what the criteria for their use is. There has to be some standards for temperature but since I don't have any idea what that is, it's easier just to keep it as a separate category. I had also broken down the stadiums by indoor vs. outdoor, but that ended up not serving any purpose, much like this past sentence.

This chart shows the incidence of hits broken down by these three criteria:

There might be a difference there, I suspect not, and I'm really not comfortable making any statements based on four years of data. This next chart shows the difference in home run incidence by the three types:

I'm not ready to make grand statements based on a sample size this small, but this data makes things look exactly the OPPOSITE of what we would expect, but there's a partial explanation that I'm not sure is as well-known as it should be. Due to a combination of park factors and weather, the coastal teams (Seattle, San Francisco, LA Angels and Dodgers and San Diego) are difficult home run parks--these are the 2012 Batting Park Factors for those parks:

Reach your own conclusions, but it would appear that the idea of cold weather vs. warm weather heating, while intriguing, might not stand up to scrutiny.