New research indicates that when the sun comes out, batting averages go down.
The study also found that day games played in bright sunshine produce more strikeouts, lower ERA's, and an increased win percentage for the home team.
Researchers from Kent State University combed through stats for more than 10,750 Major League day games stretching back to the late 80's. What they found provides indisputable evidence that a ballgame under bright sunshine will be different from one under cloudy skies, although the why of this is open to discussion.
The researchers theorize that glare and eyestrain on a sunny day make it harder on hitters. Mets third baseman David Wright is among those who buy that theory, saying "I always prefer a little cloud cover." The study did not tease out the effect on hitters of those dreadful late-afternoon games, where the mound is often in shadow but the outfield in bright sunshine. I'm guessing the hitters suffer even more in those conditions.
The study reveals another anomaly: while both teams see batting averages drop and pitching stats improve when it's sunny, the home team sees the most pronounced impact. Take a look:
- Batting average: On cloudy days, home teams outhit visitors .266 to .259. When the sun's out, the home advantage narrows (.256 to .251).
- Earned runs allowed: Cloudy-day ERA's favor the home team (3.93 to 4.50), but again, the gap narrows when the sun's shining (4.26 to 4.68).
- Strikeouts: Home-team pitchers beat the visitors in strikeouts on sunny days (6.65/game to 6.14) as well as cloudy days (6.22/game to 5.67). It's close, but the home team still sees a slightly better bump from the weather.
Here's something to ponder: the home team wins 56% of the time when it's sunny--but only 52% of the time when it's cloudy. That's a staggering number--a difference of 7 wins over a 162-game season! Of course, a team doesn't play all its games at home and it doesn't play them all in the daytime--but still, it's enough to make you want the sun shining when your team is playing at home.
Oh, by the way: the study looked at night games and games played indoors and found that while hitters fared better in those conditions than in the sunshine, they still did better under cloudy skies.
Bottom line: if you like offense, pray for a little cloud cover. But if you want the home team to win, hope for sunshine.
You can see a quick summary of the study here.