does this weather app run in the background causing battery drain?

[mdwsta4]

going from the 1st gen to a 3GS it seems as though battery life is a lot worse. i'm wondering if part it might have to do with the theme i put together; specifically the weather app. does it run in the background? figure if it did that might be causing it to drain the battery excessively.

http://images50.fotki.com/v1530/photos/5/51621/223476/photo1-vi.jpg

thanks!