What Pitchers (and Numbers) Say About Pitching in the Cold

Maybe it was the fact that she spent her formative years in Germany, while I spent most of mine in Jamaica and America’s South, but my mother and I have always disagreed about a fundamental thing when it comes to the weather. For her, she wants the sun. It doesn’t matter if it’s bitter cold and dry; if the sun’s out, she’s fine. I’d rather it was warm. Don’t care if there’s a drizzle or humidity or whatever.

It turns out, when we were disagreeing about these things, we were really talking about pitching. Mostly because life is pitching and pitching is life.

But also because the temperature, and the temperature alone, does not tell the story of pitching in the cold. It’ll make sense, just stick with it.

Jose Fernandez pitched in the cold in New York this year. He struck out five and walked three — this, a game after striking out 13 and walking one at home in sunny Miami. “I couldn’t feel anything,” he said when I spoke with him a couple weeks later in San Francisco. “I couldn’t feel the ball for the first couple of innings.” Jeff Samardzija agreed about cold-weather pitching: “The ball is a pool cue, it’s hard as a rock.”

So it’s no surprise to hear pitchers talk about their fingers in the cold. Red Sox reliever Tommy Layne told our David Laurila that “The biggest problem is that you lose feeling on the tips of your fingers,” and even if you do things to warm them up, “by the time you get out there it’s a moot point. They’re cold again. Anything below 40 degrees, you start to get that numbness in your fingers. You have to really be in your mechanics to make sure that everything is in line, in order to throw strikes.” John Axford, long-time Canadian and short-time Athletic, said that “In cold weather, my focus has been on keeping my hand warm if I could.”

For all that talk about the fingers, you’d think certain pitch types might suffer more than most. People say the changeup is a feel pitch, but recently Zack Greinke and others have admitted that breaking balls require the most feel. And so, maybe the slider is the pitch most affected by the cold. Fernandez agreed — “I’ve noticed you have a little more trouble throwing a tight breaking ball,” he said — and others have concurred, too, like Layne and Danny Farquhar of the Rays as well.

By whiff rates, they’re right.

Pitch-Type Whiff Rates by Weather

Pitch Type	Hot swSTR%	Cold swSTR%	Difference
Slider	16.1%	14.8%	1.3%
Splitter	16.5%	15.5%	1.0%
Change	15.6%	15.1%	0.5%
Curve	12.6%	12.1%	0.4%
Two-Seam	5.7%	5.3%	0.4%
Four-Seam	7.6%	7.3%	0.3%
Cutter	10.1%	10.0%	0.1%
Sinker	5.4%	5.3%	0.0%
Knuckle Curve	13.2%	13.8%	-0.6%

2015, Hot is over 60 degrees, Cold under.

But we’re not done yet, because the reason behind these whiff rates is not completely obvious. We can blame the fingers, perhaps, but why is the cutter affected so much less? The negative difference for the knuckle curve may just be a product of sample size, but why is that breaking ball on the other side of the list? What’s the hitter’s role in this?

So you ask pitchers a little more about what they do to stay warm. Pocket warmers in every pocket, joked Matt Shoemaker. Hot breath on the finger tips. Shaking the arms to keep the blood flowing. Even just running. “I like to be sweaty even before I pick up a ball,” said Coloradan Kevin Gausman to Laurila. “I’ll maybe run for an extra 10 minutes than usual. I’ll do stuff inside. Little things to get my body ready.”

But if you think that sweat is just about getting nice and warm, listen again. Some of it is just about getting loose, yes. Muscles take longer to get warm in cold weather. “In really cold weather, it seems like you need about 15 to 20 pitches to really start feeling loose,” said the Rays’ Farquhar. “Sitting around is not a good thing. You have to keep your body moving. Talking to Dana [Eveland] last night, he got cold in the dugout between innings and his first pitch, he plunked Jackie Bradley Jr. He said the eight pitches from the mound weren’t enough for him to get loose.”

On the other hand, the sweat itself has value. Axford’s strategy for the cold gets at it: “More blowing in your hands, trying to get some of that moisture on your fingers.” Samardzija puts it into focus for us, though, when he says “Normally when you’re out there, you’re sweating, and you have something to put on the ball for grip.” Sweat acts as the body’s natural grip-provider in dry, cold weather.

So, perhaps the weather is affecting their ability to get a grip on the ball. That should change the movement on the pitches. Chris Archer thought it was possible, at least, when he told Laurila that “maybe” there is a difference on pitch types “if you look deep into the data. Maybe there are a couple more inches of break if it’s warmer.”

Pitch-Type Movements by Weather

Pitch Type	Cold X	Cold Z	Hot X	Hot Z	Diff Z	Diff X
Cutter	0.58	5.94	1.27	5.58	-0.36	0.70
Four-Seam	-1.51	9.45	-1.70	9.11	-0.34	-0.19
Two-Seam	-2.75	6.37	-2.15	6.10	-0.27	0.59
Curve	2.74	-5.01	3.21	-5.07	-0.05	0.48
Slider	1.59	1.32	1.65	1.27	-0.04	0.05
Change	-1.49	4.55	-1.50	4.57	0.02	-0.01
Splitter	-6.05	2.75	-4.56	2.88	0.13	1.50
Knuckle Curve	3.47	-5.78	3.76	-5.47	0.31	0.29

2015, Hot is over 60 degrees, Cold under. X = horizontal movement, Z = vertical movement.

Huh. The slider is the least changed, really. And the pitches that did about the same in cold and warm from the table above? They get a lot less drop in cold weather. Strange.

Maybe the cold itself is changing the movement of the pitches? I asked Baseball Physicist Alan Nathan about that. “All other things equal (same speed and spin), there will be about 2.3% less movement at 40 degrees than at 90 degrees, assuming 50% relative humidity at both temperatures,” he said. He also translated himself: “That is not a very large effect and not even close to the effect due to the elevation difference between Coors and sea level (that is around 20%).”

Nathan did wonder if weather-induced poor grip on the ball was affecting the ball in a way that the movement numbers aren’t fully capturing. “As you point out, cold and dry exacerbates the slippery-ball issue, making it more difficult to get spin on the ball. Less spin means less movement,” he said. And there is a bit of a weather effect on spin, if only crudely judged by month. Here are average four-seam spin rates by month. You see that they peak with the weather.

Still, it’s not a big effect, and it doesn’t show in the movement numbers for all of the pitches. Perhaps what’s happening here is that we aren’t studying the right thing when we study only temperature. Oakland’s Chris Bassitt, who is from Ohio and hasn’t had a problem pitching in the cold (“I’ve pitched in cold forever. I’m just warm, I guess.”) does have a problem in a certain warm park in the big leagues. “I feel it big time in Arizona, when it’s dry. Lack of humidity is the worst. Cold doesn’t affect me one bit,” the starter said.

Suddenly you hear that in everybody’s responses. Ryan Dull throws a ton of sliders for the Athletics and agreed that the feel on the ball was the thing, and that humidity always helps there. Sergio Romo grew up in Colorado, and feels the slider fine in cold weather. “I do notice in more humidity that it snaps off better,” he added, though. “So it’s more about physics than feel.”

So we have competing effects here. Cold days are generally drier, yes, but they aren’t always. On a cold, wet day — the kind of day neither my mother nor I would love — pitches move well and pitchers get good grip on the ball. A cold, dry day has weather that would reduce the pitch movement just a bit, and then also makes the grip on the ball tougher to get right.

And while the pitcher is trying to struggle through all of this, the hitter’s even worse off. He loses 3.3 feet off his batted balls per ten degrees in temperature, according to Nathan. And even if pitchers can lose up to a tick on their fastball in temperatures lower than 50 degrees, as Jeff Zimmerman found, hitters may become over-aware of a certain type of fastball in cold weather.

Layne told Laurila the conventional wisdom (“Anything that has good action in on hitters is typically the most successful pitch, because they don’t want to get jammed. It hurts their hands when they get jammed”) and Jeff Samardzija agreed (“But you can pitch inside to hitters more because they don’t want that feeling of hitting the ball off the handle in the cold”).

Turns out, pitchers could take more advantage of this situation than they do. Well, lefties do some, at least. When lefties throw to lefties in cold weather, they go inside 7% more often than in hot weather. When they throw to righties, the go inside 3% more often. Righties, for some reason, throw inside just about the same, no matter the weather.

Maybe we don’t know exactly why the slider is worse in bad weather. Or if it’s actually worse in practice, or just in the heads of pitchers. But we do know that the marketplace of baseball has shown us that the slider happens less in cold weather. As Fernandez said, “A fastball, you always feel good with. In cold weather, you’re going to use your fastball more.”

He’s right, but mostly about the sinker, which gets the most love in cold weather. To wit:

Pitch Type Percentages by Weather

Pitch Type	Hot%	Cold%	Diff
Four-Seamer	36.6%	35.9%	-0.7%
Slider	16.6%	16.1%	-0.6%
Cutter	5.6%	5.4%	-0.2%
Knuckle Curve	2.0%	1.8%	-0.2%
Splitter	1.1%	1.1%	0.0%
Change	9.5%	9.5%	0.1%
Curve	7.5%	7.7%	0.2%
Sinker	7.3%	7.6%	0.3%
Two-Seam	13.4%	14.4%	1.0%

2015, Hot is over 60 degrees, Cold under.

Don’t feel bad for a pitcher out there. Not only are they living the life, but they actually probably don’t feel that cold. As Dull said, “There is an adrenaline thing, though, out on the big-league mound you don’t usually feel cold.” We aren’t whining about pitchers feeling bad on the mound.

We are talking about the way weather can affect the pitcher, though. And it looks like the cold means fewer sliders, more sinkers, a little less drop on a few pitches — and yet despite all this, the advantage still goes to the pitcher, as runs per game move slowly up as the temperature rises. Looks like pitchers side with my mother in a weird way: the temperature is irrelevant. They just want moisture.