Wind and Kickball

Its really windy outside right now.  Just something I've noticed.  But I have a question... does anyone know what causes wind?  Its something I had plenty of time to ponder during my (infinetely boring) kickball game in gym today.  Its like, you kick the ball, and then you run.  Simple, right?  And sometimes fun!  But not when the only people on your team actually playing are the wierdo preps who scream and yell 'lets go!' then try and do homeruns even when they're already out.  The best highlight of a kickball game I've ever witnessed was when a certain idiot named... oh, i cant name names on the internet, so we'll call him the "Wierdo", got slammed in the stomach head-on with a kickball some prep girl he was pitching to kicked... it was hilarious, especially the part where he rolled around on the ground in fake (im assuming) agony...oh, crap, now ive lost my train of thought. oh yes.  Wind. What makes it.  If anyone finds out, put it in a comment and post it, ok? cus im curious.