- FanGraphs Fantasy Baseball - http://www.fangraphs.com/fantasy -

Relevant Fantasy Weather Data

Batters always seem to heat once summer rolls around. While some players may like to play in the summer versus the cooler months, the warmer weather also increases hitter production. Over the the rest of the year, our authors will be giving our readers a heads up for any possible games which may be hitter or pitcher friendly.

Weather has a significant effect on the distance a ball travels. In his book, the Physics of Baseball, Robert K. Adair noted a 10 degree temperature increase leads to an extra four feet on a 400-foot fly ball and each one mile per hour following wind speed means an extra three feet. For example, a fly ball hit at Wrigley field will travel 38 feet further on a day with the wing blowing out five mph and at 80 degrees versus an early spring day when the wind is blowing in five mph and the temperature is 60 degrees. This information shouldn’t be used to start Wade Davis over King Felix, but if an owner is deciding between a couple of similar players, it could be used as a tie-breaker.

Starting with temperature, I looked to get an accurate yet simple formula to see when the run scoring environment changes. Taking all the team scores from 2007 to 2013, I grouped them into five degree temperature ranges. Here are the findings:

Fewer samples existed under or equal to 65F, so I grouped all the values together and calculated the average value. Teams and their pitchers look to give up an extra run when the temperature is 100F or more versus when it is 65F or less.

The daily temperatures can be found at DailyBaseballData.com and our authors will be looking looking at publishing the extreme values when they occur.

Another run-scoring weather factor is the wind. I looked at all the stadiums when the wind was blowing out for a change in the run scoring environment. Not all stadiums were effected by wind because of design or local weather patterns. Here are the instances where the runs scored changed by 0.5 or more compared to the average.

Wind blowing out RS Diff
Chicago (NL) +1.0
Wind blowing in
New York (AL) -0.8
Philadelphia -0.6
Chicago (NL) -0.5
Texas +0.5

Today, I am just going to at the most extreme case, Wrigley Field. Finding a simple way to show the different scoring environments in Wrigley was not so easy. Two factors were at work. When the wind blows in, the average temperature is over 10 degrees cooler than when the hot summer wind is blowing out. Also, twice as many games are played with the wind blowing in than out.

I cut and diced the data way too many ways. Finally, I came up with the following chart for dealing with games at Wrigley:

Wind Direction R/G AVG Temp. AVG Wind # of Games
Out >= 74 6.0 82.3 9.2 79
Out <= 73 4.9 62.3 9.8 44
In 4.1 64.0 8.6 259

If the game is hot and the wind is blowing out, hold on for a high-scoring game compared to when the wind is blowing in. Again, our authors will give our readers a heads up if the wind is blowing out at Wrigley.

I am going to dig a little deeper to see if wind patterns affect any other parks. For now, games are generally being played in the normal zone as the temperature moves from cool spring temperatures to the heat of summer.