I went to Warped Tour last summer in Austin, Texas and it started raining. I was actually really glad. It's REALLY fucking hot in Austin.
But you get soaked and it's cold. What's fun about that?
I disagree. What's not to love?
When you're sweating, dancing, screaming, and (depending on the genre) moshing? As long as the equipment was under some sort of roof, that'd be awesome.
I went to this John Mayer concert last year. It was raining when we drove to the venue but eventually stopped when we got there so we didn't bother to bring our umbrellas. Big mistake. It started pouring like 20 minutes later the concert started.