When betting on the total in a major league baseball game one of the biggest misunderstood factors used to handicap whether the game will go over or stay under the total is the weather itself. Everyone has seen the way the wind blowing out at Wrigley Field can turn a normal game into a homerun derby. Many people think the thin air in Coors Field is automatically good for an extra two runs per night, or conversely how the dead-sea air of McCovey Cove at AT&T Park is where balls die in the gaps. There’s no doubt that weather can affect a ball game, but how much influence it has is worthy of debate.
In order to truly understand the affects of weather on a hit or thrown baseball, one must understand the physics of a hit or thrown baseball. Neglecting weather for a moment, when a baseball is flying freely through the air it is affected by two major forces: gravity and friction. Gravity pulls the ball down and has the same affect on every ball, but the friction component (or drag force) varies depending on the properties of the air it’s flying through, properties like air temperature, pressure and humidity (i.e. the weather). The temperature, pressure and humidity will work together to change the density of the air. The less dense the air, the less air molecules are around to exert their drag force on the ball and would therefore result in a greater distance of flight.
So in other words, if the temperature, humidity and pressure are all the same and constant, the ball will travel further in the less dense air of Coors Field then it will in the more dense air of Yankee Stadium.
Apply the math and you will find a baseball will travel 9 percent further in the less dense air at Mile High Coors Field then it will at sea level in Yankee Stadium. So a 400-foot shot at Yankee Stadium would travel about 436-feet in Coors Field, providing the factors or temperature, pressure and humidity are all EQUAL. How often are these weather factors equal in both parts of the country? It’s not just deep fly balls that are affected by the air density, so is the thrown ball … and the way fielders run after the baseball too.
A pitcher’s fastball will get to the plate faster in the less dense air at Coors Field and have more zip on it, but his secondary stuff like curveballs, sliders and cutters/splitters won’t have the same break because the less dense air has less frictional drag (what causes a curve to actually curve). Some studies have shown up to a 3-inch difference in a breaking ball at sea level when compared to higher elevations.
Outfielders deal with issues too. Less frictional drag means a batted ball will get into the gaps quicker in Coors than in Yankee Stadium, making the outfielders seem like they have more ground to cover but less time to do it. Again, studies have shown that the difference in range is as big as a foot for infielders at Coors, and up to 9 feet for an outfielder when compared to a sea-level park.
Keep in mind that all of the physics and math described above depends on one important factor … a host of weather variables being equal or constant. This is never the case, which is where handicapping of the weather elements takes it form.
The temperature at the ballpark any given day will affect the flight of a baseball. Again, providing the other variables are equal, a baseball will travel further in hot weather than in cold weather. But it takes pretty drastic differences in the temp to see substantial differences on the field, as a ball hit in 45-degree weather will only travel about 20 feet less than the same ball hit in 95-degree weather, so a full 50-degree difference in temp results in only a few extra feet off the bat.
Humidity is also an often-misunderstood weather factor, especially since most people equate those hot, sticky days in mid-summer as homerun weather. But while humid air is actually less dense and should provide for less resistance and greater distance, the humidity itself affects the ball by making it less elastic and heavier, so in reality the ball travels slightly shorter in humid air then in dry air.
And we haven’t even begun to discuss the single most important influence on the trajectory of a baseball once it is hit (or thrown) … the wind. You don’t need to be Einstein to figure out that the wind will blow fly balls into homeruns, knock homeruns down into long outs, or push balls further right or left than its trajectory would be under calm conditions. The wind blowing out reduces the frictional drag and allows the ball to travel further, but a strong wind blowing in will increase the drag and keep balls in the yard.
But just like in the case of temperature, it takes a pretty significant gust of wind to have significant affects in the baseball’s outcome. Studies have proven that a ball hit 400-feet on a calm day will turn it into a 445-foot drive, but it would need a 15 mph gust blowing in order to add that much distance.
It’s also hard to “beat” the oddsmakers in Las Vegas in regards to the wind. They are checking it’s direction and speed too, just like you, so it’s not like it’s a secret. Oddsmakers will adjust the opening totals accordingly, so any advantage you get by playing meteorologist for more than a few minutes is usually negated anyway.
So if you’re still reading this, I’m sure you’re waiting to find out how to use all of this information about the weather to help you handicap baseball games and win more bets on over.
What I’ve tried to point out is that unless every game is played inside a test tube, with all of the variable the same, it’s extremely hard to relate the weather and its affects in any meaningful way to more (or less) offense.
While it’s nice to know ahead of time if the wind is blowing out, or in, or if the temperature is really high and the stadium is surrounded by a low pressure mass … in the end the weather needs to be so drastically different (strong winds, really high temps, high levels of humidity) in order for it to have an recognizable affect on the outcome.
I recommend spending the time to see what the weather forecast is for a game you might be wagering on the over/under total, just to make sure you’re not getting into a bad deal, but there are much more influential factors to consider when handicapping baseball games for totals like ballpark factors, pitching stats and umpires and their strike zones.