definitely take lens wipes, and even a chamois (absorbant towel) as well, to wipe off your hands if they get too wet.
ideally, you'd get a waterproof "bag"... they can cost quite a bit, and since the show is tomorrow, it's doubtful you could get such an item in time.
i'm not guaranteeing this to work, but it can't hurt (definitely better than risking ruining your camera - because if water gets into the circuitry, it could screw up the camera nicely)... take a 1-gallon ziplock bag, cut a small hole - just big enough for the lens head to fit through - and gently push the lens head through the hole. that way, only the lens is "exposed" to the elements. obviously, you'd want the open end of the ziplock bag facing downward (and this will make it easy for you to access the controls on the cam).
will you be using a tripod, or just handheld shooting?