There is a standard "let's make a rainstorm" that kids at camp and kids with clever music teachers do. It involves doing the "wave" across the room but instead of hands in the air, its body percussion (snap, clap, pat and variations) building from silence to a big storm.
It was a part of my plan today with the words "giant paper?" penciled next to it. Not prepared to really go there, I walked into the teachers lounge and saw a giant pile of ugly orange poster board for giveaway. If creativity is putting two "knowns" together to make a new known then I win today.
We didn't have a thunderstorm, we had hurricane winds with practically on top of us thunder (when they started kicking and punching the paper). It was awesome.