Damn there he is holding an umbrella over his head as he announces The Pointer Sisters, right here on youtube, Capitol Fourth, 2001:
http://www.youtube.com/watch?v=Ntc7dV4IE6Q
At 2:45 or so, the shot from the back of the stage shows obvious recent rainfall; by 3:30 you can see lots of wet hair and shirts everywhere, and by 4:00 the rain is pounding down so hard that The Pointer Sisters are not just soaked but holding umbrellas as they sing.
*ping* yep here is video of just that, I’ll tell you the truth I didn’t get all the way through the video and had to get myself a belt of bourbon like one of the stereotypes in a 1960’s sitcom.