As I am currently out of the Cubs viewing area I decided to look into something during today's dismal performance. We seem to have been having serious trouble scoring runs since about mid to late may. Coincidentally, Chicago has been experiencing unseasonably cold weather from that time frame, so I decided to do a little experiemnt.
Using a variety of sources (weather reports from weather.com, the national weather service, farmer's almanac as well as game summary data from the official Cubs site and game time information from here) I decided to graph our recent run scoring perforamnces (home games since mid-to-late May, as well as the 3 games at the Cell since they were also played in Chicago) vs. the difference (in degrees) of the game time temperature for that day and the normal (as defined by the national weather service) termperature for that day.
I did a little rounding to eliminate decimal points, but what I found was rather interesting. Simply, the Cubbies don't do so well when its unseasonably cold out. Almost all of our offenseive droughts have occured on days when the game time temperature is 5 degrees or more below the normal temperature for that date. With one exception, all of the games in which we've scored a plethora of runs (5 or more) have happened when the game time termperature outside has been at or above the "normal" temperature for the date.
So, I guess, from now on instead of shouting "Let's get some runs!" during the 7th inning stretch, we should instead be shouting "Let's get some sun!"
Here's a quick and dirty chart of the data: