Course No. MLB 103
In general, the weather is a huge factor in MLB DFS games. First and foremost, PPDs are the most important factor by far. If a game where you use any players, especially a SP, is rained out, you most likely will not be able to win.
Delays are important for SPs, especially if they are long lasting and/or occur early in the game. With millions of dollars invested in each SP, teams will do whatever they can to try and prevent injury and a great way to get a SP injured is to send him back into the game after sitting around after a 60 or 90-minute delay.
Another huge way weather can impact MLB and DFS games is the wind. A wind blowing out will favor the batter and one blowing in will favor the pitcher, especially at speeds over 10 mph.
The last, and probably the most complicated, way that weather can impact MLB games is air density. Simply put, low air density means that a batted ball can travel farther than if the air density was higher. The reason is that is friction as air density refers to the number of air molecules per a specific space (scientifically known as volume). The less air molecules a ball runs into, the less energy is wasted as friction and the farther it can travel.
Air density is influenced by three factors, elevation, temperature and humidity. Elevation will never change when talking about the same ballpark. And this is where Coors Field in Denver stands head and shoulders above any other MLB ballpark. At over 5,000 feet in elevation, and with no other MLB park even close to 2,000 feet, Coors always has a huge advantage in terms of low air density. Numerous studies have been dome on the influence Coors plays on batted balls and a conservative estimate is that a batted ball will travel at least 9% farther here than at a ballpark near sea-level, such as Fenway Park in Boston. The elevation of Coors will far and away dwarf any other weather factor and this stadium.
Temperature and humidity play about equal parts when compared to each other and their roles are easily described. That is, the warmer and the more humid the air is, the lower the air density. Though these two factors do not play quite the same role as elevation does, these factors are noticeable and meaningful.
Probably the easiest way weather can influence a game (besides PPDs/delays) is when all of these factors are working together. For example, a hot and humid day at Coors with the wind blowing out to left at 20 mph is obviously a hitter's paradise. There is also the yin to this yang, a wind blowing in at 20 mph with temps in the low 40s on an April evening at Fenway can be said to strongly favor the pitcher.
Another factor to try to consider, though it is very difficult to do, is to factor in a player's particular history in the cold or heat. Maybe a player is from a southern climate and does not like playing when it is cold, or vice versa. Pitchers are said to favor cool weather, but if it is too cold, the pitchers can lose their “feel" for breaking pitchers or they lose their grip on a fastball.
Similar to this is that curve balls are said to be tougher to control or grip at Coors. The lack of air density gives the ball less bite and breaking pitches do not break as well. Another factor is that people say that knuckleball pitchers prefer humid weather and a wind blowing toward them as that makes their pitches move more. All of these factors are very difficult to prove as you cannot really put a scientific study on to these things.