if it had a effect on the ball then it would possibly make a difference, like hitting a flyball that may go yard usually but in the rain it may just drop.
but the thing i hate the most. is when you're playing in closed roof park and its rain outside and the commentators are talking about how lucky they are they are in the booth and not down on the field. ummm hate to break it to you commentator but the roof is closed there is no rain on the field.