Who to Bet When the Mercury Rises

Baseball is played outside … in the summer. Inclement weather and extreme heat often have an impact on how MLB games are played.

The Astros, Blue Jays, Brewers, Diamondbacks, Mariners, Marlins, and Rays play in stadiums with roofs – allowing them to have perfect weather conditions for every game.

The other 23 teams must rough it in the great outdoors and sometimes it gets pretty hot. Who has the advantage on those hot, sticky days? Are the home teams prepared for it? Does the heat help underdogs? Does the total tend to go over or under?

Killersports MLB data includes temperature at game time and will help answer these questions.

Do I Bet Home or Road Teams During Hot Games?

When the temperature rises above 90 degrees fahrenheit at game time, the road teams seem to have a small advantage. Here are the numbers that road teams have put together in hot games since 2014.

Year	Winning %	Profit
2019	53.8%	$758
2018	50.3%	$80
2017	38.5%	-$1,755
2016	44.9%	-$321
2015	45.1%	-$954
2014	60.9%	$2,801
Total	48.4%	$609

Road teams do seem to perform a bit better in these situations – probably because the home players do not want to leave their houses when it gets this hot.

I tried narrowing the criteria to even hotter games (i.e. only 95+ or 100+). The win rates do improve for road teams but the sample size shrinks so profits will be lower. For example, there have been 700 games since 2014 in which the game time temperature was at least 90 Fahrenheit but only 34 in which it was at least 100.

Rule of Thumb: When the temperature is at least 90 Fahrenheit at first pitch, the road team has a small advantage. 95 or 100 is preferred.

Do I Bet Favorites or Underdogs During Hot Games?

Is heat the great equalizer which gives underdogs a chance or does it exaggerate the gap in talent between good and bad teams? The data suggests that heat does neither.

Here is a quick look at how favorites have fared in games with a temperature of at least 90 Fahrenheit. Notice how there is no trend to speak of.

Year	Winning %	Profit
2019	57.0%	-$456
2018	61.4%	$1,060
2017	60.4%	$833
2016	57.8%	-$843
2015	59.0%	$349
2014	57.6%	-$380
Total	59.0%	$65

I thought I was onto something when I raised the criteria temp to 95 Fahrenheit and found that favorites are quite profitable in that 95-99 degree range. I then found favorites are a losing bet if the thermometer reaches 100.

This makes no sense and tells me that there is no temperature-related advantage for favorites or underdogs.

Rule of Thumb: Heat should not factor into a favorite-underdog decision.

Do I Bet Over or Unders During Hot Games?

The adage I’ve always heard in baseball is that teams will swing early and often and give away at-bats in hot games just to get off the field. I take this to mean we should bet the under, but I want to see what the data says.

Here are how unders have performed since 2014 when the game time temp is at 90 Fahrenheit or above.

Year	Winning %	Profit
2019	49.4%	-$514
2018	43.6%	-$2,543
2017	43.5%	-$1,562
2016	50.3%	-$550
2015	47.2%	-$990
2014	50.6%	-$290
Total	47.3%	-$6,449

I thought that maybe 90 degrees was not hot enough. Maybe unders did not start profiting until it got really hot. I checked the same stats at 95 and 100 degrees and still found no trends.

Also, just because the under has lost money in hot games since 2014 does not mean that overs are profitable. The over is super inconsistent, profitable in just 3 of the past 7 seasons.

If hitters really do give away more at-bats in the heat, Vegas must account for that in their totals.

Rule of Thumb: Overs are a better bet than unders in hot games, but neither is a confident bet.

I’m always trying to find new angles to attack the books. See you on top!