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How might record heat affect Fall Classic?

Expected 100 degrees would make for hottest World Series
MLB.com @mike_petriello

The first game of the World Series in Los Angeles tonight is almost certainly going to be the hottest in Series history, and we're not just talking about the fact that it's the first time since 1970 that two 100-win teams are facing off. The current forecasts call for 100 degrees tonight, cooling to a relatively balmy 97 degrees on Wednesday for Game 2. You're going to hear endless comments about how "the ball is flying out of here." Is it true? And what effect can the heat really have?

If it really is 100 degrees -- at least at the start of the game, which is when the official temperature is marked -- it would set a World Series record. Among games with reliably tracked temperature data, there's never been a Fall Classic game with a temperature tracked at or above 95 degrees, with Game 1 of the 2001 World Series (Yankees at D-backs) coming in atop the list at 94 degrees. And yes, the roof was open.

The first game of the World Series in Los Angeles tonight is almost certainly going to be the hottest in Series history, and we're not just talking about the fact that it's the first time since 1970 that two 100-win teams are facing off. The current forecasts call for 100 degrees tonight, cooling to a relatively balmy 97 degrees on Wednesday for Game 2. You're going to hear endless comments about how "the ball is flying out of here." Is it true? And what effect can the heat really have?

If it really is 100 degrees -- at least at the start of the game, which is when the official temperature is marked -- it would set a World Series record. Among games with reliably tracked temperature data, there's never been a Fall Classic game with a temperature tracked at or above 95 degrees, with Game 1 of the 2001 World Series (Yankees at D-backs) coming in atop the list at 94 degrees. And yes, the roof was open.

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"The first couple of [NLCS] games here vs. the Cubs were really hot [84 degrees in Game 1 and 92 in Game 2]," said Dodgers utility man Charlie Culberson. "I'm from Georgia, I'm from the South. We're used to it. We've played in it. I don't think it's really going to affect us, it's the World Series, it doesn't matter. We'll be ready."

As for Games 1 and 2 of this World Series presented by YouTube TV, the bottom line is this: It's going to be hot, though with low humidity.

The first thing you're going to want to know is if this is really going to make the ball go farther. It is. Probably.

Heat adds offense

Fortunately for us, a great deal of study has been done in this arena, starting with the work of Dr. Alan Nathan, professor emeritus of physics at the University of Illinois at Urbana-Champaign. His research figures have indicated that for every 10 degrees of added temperature, a ball may be expected to travel 3.3 additional feet.

As the average high in Los Angeles at this time of year is 77 degrees, it's possible that on a 100-degree day we're seeing approximately seven more feet of distance. That could turn a warning-track fly ball into a home run, potentially. But while the physics themselves are instructive, we have many games of actual data to look at. What's actually happened as weather gets warmer?

As expected, the offense benefits. In 2017, the Majors slugged .391 in games where the temperature was 59 degrees or below. They slugged .479, nearly a hundred points higher, at 90 degrees and up. That's the equivalent of Kole Calhoun at the low end and Corey Seager at the high end. That's a big deal.

Home runs went up, too. Just 3.1 percent of at-bats ended in a home run at the coldest temperatures; 4.4 percent did at the warmest. (If that doesn't sound like much, realize that there were more than 185,000 plate appearances this year; a 1 percent change affects thousands of outcomes.) Runs per team game were just 4.29 at 59 degrees and below, up to 4.51 between 70 and 79 degrees, 4.91 between 80 and 89, and a massive 5.47 above 90.

That backs up the physics. Of course, that's one year, across all stadiums. Tonight's game won't be at the high altitude of Colorado or with the short fence in Yankee Stadium or anywhere else. What's happened in Dodger Stadium, specifically? Let's go back to 2000 to find out. Unsurprisingly, the effect holds.

In the 21st century, teams score 4.36 runs/game at Dodger Stadium when it's above 90 degrees at game time, dropping steadily to 3.85 runs/game when it's below 60. Slugging percentage is .416 when it's hot out, and .364 at the bottom. When it's hotter, the offense does benefit -- and remember, we've sorted these bins with "90 degrees" starting the hottest section, because there's just so little data on games over 100. 

That's partially because of the changes in the air noted above, becoming more favorable to batted-ball distance. But it's also likely that there's a fatigue effect from working at such high temperatures, though Dodgers manager Dave Roberts didn't seem to think so.

"Fortunately, we've had a great year of weather. In Los Angeles, I think our estimation of hot is still relative to being in Southern California, being near the coast," Roberts said. "And the guy taking the baseball for us, I don't think he's concerned about a little spike in heat, so we feel good."

That's about what you'd expect from a manager preparing his ace for his first World Series start, and Clayton Kershaw's history in hot weather has been limited, as he's made a start in weather at 90 degrees or above just three times in the last four years -- though he's been very good, allowing four earned runs and 29 strikeouts in 23 innings.

It's more difficult to make that comparison for Dallas Keuchel, given that the data isn't readily available on whether Minute Maid Park has the roof open or not, but it's worth noting there's a small potential advantage here for him. The Astros' ace led the Majors in ground-ball percentage, at 67 percent, and balls on the ground rarely fly over the fence.

But as great as these two are -- and they are -- they're both lefties, pitching on an extremely hot day, to two of the five best lefty-mashing teams in baseball, with rested bullpens. If they don't go deeply into this game, it won't be a failure. It'll be an expectation.

Remember, heat won't make Dodger Stadium play like Coors Field. Temperature can't affect a batted ball in the same way that altitude can. But it's going to be hot, and it matters. The ball's going to go just a bit farther. Depending on the circumstances, it might make a fly ball a slightly different kind of fly ball -- or, it might help create the home run that turns the Series.

Mike Petriello is an analyst for MLB.com and the host of the Statcast podcast. He has previously written for ESPN Insider and FanGraphs.

Los Angeles Dodgers, Houston Astros, Clayton Kershaw, Dallas Keuchel