We often hear about players who start slowly attributing it to the colder weather. Science gives us good reasons to believe that offense should rise as the temperature does. Robert K. Adair’s great book The Physics Of Baseball has a good explanation of why balls carry farther in warm air than in cold, for example.
However, is it the temperature that causes the difference, or simply a player getting used to his in-season regimen and routine? Since the cooler days tend to occur at the beginning and the end of the season, it will be hard to separate the climatic effect from personal adjustments and work habits.
Let’s speculate for a moment that there are players who are more sensitive to temperature than other players. Now, if offense as a whole is up during warm weather, we shouldn’t be surprised that any individual player plays better in the heat. As a baseline, we would expect a certain amount of increase from any player. What we’re really interested in is whether players tend to gain more (or less) than average from year to year.
We know that baseball is a different game in April. For the most part, a pair of dominant starting pitchers can face each other head-to-head a few times through the rotation, because the best starters are used in descending order according to skill set. Hitters are still working on timing the pitching and getting into playing shape.
One of the aspects that effects the early part of the regular season is the cold and damp weather which can plague cities all across the landscape. In most parts of North America, atmospheric conditions are significantly different in April than during the summertime when most of the regular season games are played. As the baseball season continues to lengthen, Major League Baseball increases the possibility of extreme weather conditions affecting one of the most important baseball games of the season, opening week. Important to both the fans who wait to watch baseball all winter and to the stat-heads who try to project season numbers.
Two of the first three games the Indians were scheduled to compete in 2016 were postponed due to “inclement” weather with one that has yet to be made up. For those living in Northeast Ohio, “inclement” can easily be interchanged for “miserable.” Rain, sleet, snow, wind and unusually low high temperatures were the reason why fans have to wait a little longer to enjoy baseball. In the two games that were played, the average temperature was 31 degrees with a windchill nearly half that number.
How does the air temperature affect the game of baseball? I have sampled 100 major league games from the 2014-2015 seasons and am beginning to analyze the relationship between game time weather conditions and pitchers’ statistics. The following overview breaks down some pitching statistics by air temperature.
Pitchers tend to strike out a higher proportion of batters in cold weather. I’m not quite sure why this is, particularly because pitches should move more and be more difficult to hit in warm, humid weather. I expect a pitch to move more when pitchers are able to grip a ball securely in warm and humid weather, but all other things being equal pitches will actually move more in cold, dense air. Pitchers do get to wear jackets and stay warm when they are not on the mound and they also have the benefit of warm-up tosses and constant activity during their half-inning of work. Pitchers might stay warmer and be less affected by coldness than hitters.
Pitchers tend to walk more batters in cold weather. Many pitchers note that baseballs feel “hard” and difficult to grip in cold weather. Football players say the same thing about the pigskin in winter. It’s likely that dry cold air leads to imprecision in control, particularly when pitchers are working with “feel” pitches like curve balls and change-ups.
What about hitting batters? The ball stings a little bit more in cold weather, so I anticipated a decline in hit by pitch rates in cold weather to reflect the hitters’ increased effort to get out of the way of inside pitches. As it turns out, hit by pitch rates actually increase in the cold weather. This is more evidence that pitchers’ control suffers in cold weather. Home runs are relatively rare in cold weather. Over 4% of batted balls leave the ballpark in 75 degree or warmer weather, but that rate drops to about 3.2% in the kind of cold weather conditions we are witnessing so far this April.
Additionally, batted balls in play are less likely to lead to hits in cold weather when compared to more moderate or hot temperatures. The most straightforward explanation for these findings is that the ball simply does not carry very well in cold weather. Batted baseballs are slowed down by air resistance in the heavy, dense air of cool April nights.
Pitchers generally have worse control, but higher strikeout rates and better luck with balls in play in cold weather. I’m not sure if this favors a certain type of pitcher in the post-season. It might be the case that a pitcher’s “stuff” is an important factor in how the weather interacts with their performance. For example, a pitcher who relies on breaking balls or change-ups and are susceptible to control problems might be at a particular disadvantage in cold weather conditions.
From an offensive perspective, this evidence suggests patient lineups will fare well in cold weather when compared to free swinging lineups. Pitchers appear to throw fewer strikes in cold weather and a patient lineup may be more likely to take advantage of this result. Additionally, a batted ball is less valuable in cold weather than warm weather because a batted ball is less likely to fall for a hit or clear the outfield fences in below-55 degrees conditions.
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