I don't get why all the new stadiums being built on the east coast don't have retractable roofs. I know it's more expensive, but think about the money you lose in other areas. Concession would do better. How many less people come to the park or leave early when they're "getting a game in" because of the rain or it's 100 degrees and people leave early or don't come at all?
You could also use the stadium year round for concerts and what not.