When the weather heats up do hitters really get hotter?
Recently Brandon Nimmo of the Mets was interviewed by Steve Gelbs of SNY and Nimmo made mention that the weather was heating up and he and the team would continue doing the same. Baseball players have belief that warmer weather leads to hotter bats leading to the baseball flying further. What kind of evidence exists that this is true? I was curious and looked around.
The Science of Baseball flight
From a 2023 Article in Scientific American:
‘The physics tell a simple and compelling story: Warm air is less dense than cool air. As air heats up and molecules move faster, the air expands, leaving more space between molecules. As a result, a batted ball should fly farther on a warmer day than it would on a cooler day owing to less air resistance’
Blah blah blah, I’ve read stuff like that a thousand times. Shoulda, woulda, coulda, stuff.
The Scientific American article went on to note:
Based on data between 1962 — when Mickey Mantle was American League MVP and Willie Mays topped the home run chart — and 2019, we found that a game that is 10 degrees Celsius (18 degree Fahrenheit) warmer than the average game would have nearly 20% more home runs than average.
Hmm. I think we might be getting somewhere.
According to Alan M. Nathan, author of The Physics of Baseball, ‘every 10 degrees above 75 degrees can help a baseball travel about three feet farther, when all things are equal. When it’s 95 degrees, the ball should travel six feet farther. That may be just enough for a ball caught at the wall to become a ball that goes over the wall.’ A ball hit to the warning track on a 75-degree day in April becomes a home run on a 95-degree day in July.
Going deep and deeper
A 2023 Article in the Washington Post went into even greater detail:
“For every 1 degree Celsius (1.8 degree Fahrenheit) increase in temperature, the number of home runs in a game increases by 1.96 percent, according to a study published in April that analyzed home run and weather data from more than 100,000 MLB games between 1962 and 2019. The study found that more than 500 home runs since 2010 can be linked to climate warming, and that the phenomenon could account for an additional 130 to 467 home runs per year by the end of the century, depending on how much the planet warms.
2020 data also from the Washington Post: Fair skies, foul balls: How weather influences baseball
‘A Washington Post analysis of MLB data supports the notion that balls fly farther in the summer months. Since 2006, the average number of home runs per game climbed from 2.10 in April and May to 2.20 in June, July and August. The average distance of “barreled” flyballs showed a similar trend, increasing from 387 feet in April and May to 390.6 feet in June, July and August. “Barreled” balls — well-struck balls that meet certain exit velocity and launch-angle criteria — were chosen because they are all hit similarly, helping to isolate the effects of external factors such as temperature.”
So far in 2023, the average distance of barreled flyballs increased from 385.5 feet in April and May to 387.3 feet in June and early July, while the average home runs per game climbed from 2.30 in April and May to 2.34 in June and early July.’
I was not prepared for a Global Warming discussion as it relates to baseball and prefer to leave that one alone. However, are you completely convinced yet? A 1% increase in fly ball distance even if isolating temperature is small enough to be explained away with considerations such as hitters are more in the groove and pitchers are more tired in June than they were in April or May. There needs to be more. So, I kept digging.
A weather man thinks he has some answers and a website to boot
The Washington Post article mentioned that NASA meteorologist Paul Dorian has a free website displaying the Home Run Forecast Index at each MLB park. It’s used more by fantasy baseball players and those that enjoy wagering. Dorian notes in the article that:
“There is no doubt in my mind that weather impacts baseball more than any other major sport”.
NFL players in certain cities like Chicago, Green Bay and Denver might beg to differ. Not to mention pro golfers and amateur ones too.
More from the WaPo article:
Results from the 2022 season published on the Home Run Forecast website show that games registering an index of 9 or 10 corresponded to a higher average number of home runs (2.61) and runs scored (10.04) per game, while games registering an index of 1 or 2 corresponded to a lower average number of home runs (1.40) and runs scored (7.51) per game.
“The results of the 2023 season so far are also very encouraging with similar trends to 2022,” said Dorian, who added that the average index through July 3 has been lower this year (5.27) compared with last year (5.60) due to this year’s (2023) relatively cooler April, May and June in many locations.
The evidence is becoming more convincing. But baseball is not only about home runs. I wondered how does weather impact hitting and scoring aside from home runs?
In 2023 MLB teamed up with Weather Applied Metrics, which provides weather analytics to the sports industry, to calculate the observed and predicted effect of wind on flyballs. “In cases where the hit apex is extremely high, WAM analysis has shown that the change in landing location due to wind can approach 100 [feet] in the most severe conditions,” a story on MLB’s technology blog explained.
Whoa! 100 feet is a lot on a baseball field! Tampa has the only domed stadium in MLB without a retractable roof. You will find Tampa near the bottom of the Home Run Forecast despite that Tampa is one of the hotter cities in the U.S. Colder weather cities like Milwaukee, Chicago, Toronto, Seattle, Cleveland and San Francisco are also routinely lower on the list on average. Milwaukee and Toronto have retractable rooves. The other three do not. There is irrefutable evidence that if anything, warmer weather makes the ball go further, but does it lead to better hitter outcomes overall? Are there some bloop hits that would normally fall but instead land in the glove of an onrushing outfielder?
Here’s a very nerdy chart that comes from a law journal abstract:
The apparent temperature of each game was defined as the average across a 4-hour span. This time span was used because the average duration of a game was approximately 3.5 hours in 2018 and 2019
Cold — less than 70 degrees F
Warm — 70–82 degrees F
Hot — 83–92 degrees F
Extremely hot — above 93 degrees F
The first thing you might notice is that baseball games are played in ‘hot’ weather by more than the other three categories combined. Hot weather produced a few more bases on balls, substantially higher isolated power, and 63% more home runs in extremely hot weather versus cold weather.
Unsurprisingly strikeouts are relatively unimpacted by temperature. Also interesting is that batting average on balls in play was slightly less in hot weather than it was in cold weather, but overall batting average was minimally impacted by cold, warm, or hot weather. Only in extremely hot weather did batting average spike. Think about pitching on a 95+ degree day whether it is humid or not. It is much more debilitating to pitch on a day like that than bat.
What players should be thinking and saying is that hitting on an extremely hot day is to their advantage. The correlation between players heating up once the weather does is not as strong as hitters would like it to be! But it’s a nice thing to think about when standing at the plate on a hot afternoon in July.
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About the Author: Mark Kolier along with his son Gordon co-hosts a baseball podcast called ‘Almost Cooperstown’. He also has written baseball-related articles that can be accessed on Medium.com and Substack.com.
