You may remember a few weeks back, we took a look at the relationship between temperature and length of game. From that conversation, a few readers reached out and surmised that the reason that hotter games tended to last slightly longer may be because more offense happens in games with warmer weather. Like last time, we’ll start with the 2016 data, then extend it out to 1952-2015. And because it was brought up last time, temperatures have remained almost exactly steady overall since 1952, so no need to challenge the data on the grounds of global warming.

In regards to the 2016 data, we have two problems. First, there’s still a relatively small sample size. When you only look at temperatures that have more than 20 games played, you get a range of 52-91 degrees. With a normal distribution (roughly), the peak of the temperatures sits in the low 70s with about 75 games each. So inherently there are going to be some larger swings in the numbers. The second problem we run into is that my scrape for 2016 is only pulling runs, and not hits. The 2016 data isn’t nearly as interesting as the full 60+ years, so I will save myself the hours of scraping hit data for this season. So let’s take a look at 2016, shall we?

What we see is a loose correlation between increased temperatures and runs scored. With an r2 of around .42, the relationship seems pretty loose that roughly every 20 degrees of temperature increase, you get an additional total run scored per game. That seems to jive with the findings from the time of game, that games have been slightly longer as temperatures have increased. But it gets really interesting when we magnify the data and take the full data set of 1952-2015, and we add in hits. Let’s look:

Now we’re able to look at over 73,000 games over the course of seven decades. Once again, I’ve removed the tails of the distribution and only included temperatures with more than 100 games played. Looking at the data, we see that the line smooths out dramatically, and with it we see that warmer temperatures still bring more runs, though at a slower rate than we’re seeing in 2016: about one extra run for every fifty degrees, and one additional hit every 25 degrees. Interestingly, the correlation rises dramatically to above .79 for the runs, and an astonishing .92 for hits, suggesting the relationship is a bit more intertwined than we saw with the 2016 data.

So why does the correlation exist? Here are a few theories. If you have your own, or want to disagree, be sure to leave a comment:

Pitcher game fatigue – As temperatures go up, I suspect pitchers do not last as long, having to labor in the warmer temperatures. This certainly affects pitchers more dramatically than hitters, who aren’t in as physically demanding of a situation. Thinner air – Given constant pressure and humidity, a temperature difference between 40 and 90 degrees Fahrenheit results in nearly 10% lower air pressure. In theory, this should make more outs into home runs, and could even turn balls hit into fielding gaps from singles to doubles if they’re able to make it past the fielder quicker. Scouting – In general, as the baseball season progresses, temperatures rise. This obviously peaks in August or so, but even September baseball is not nearly as cold as April baseball is. And, as the season progresses, it’s likely that scouting reports on pitchers will get more robust, which should give batters a better chance of making contact. This brings us our next point… Pitcher season fatigue – As the season progresses, pitchers begin to wear down after getting into their second century of innings pitched (for starters), or after making numerous appearances as relievers. Bats, on the other hand, tend to not be as affected by fatigue, for similar physical reasons as mentioned in the first point.

All in all, it seems that temperature has some slight effects on both pace of play and, likely related, overall offense. The dog days of summer bring with it some additional bats, and a slight bit more carry to batted balls. So next time you’re sweating it out in 90 degree temperatures, appreciate the fact that you’re getting to see a little more offense than you would have had the game been a little more comfortable.