I've been to Las Vegas a fair few times and have noticed quite often that people fail to take elementary precautions in the 'everyday' heat of 42/43 degrees, so that I want to say - Hello, people, has anyone noticed that despite appearances We Are In The Desert? I blame the prevalence of fierce air conditioning, which is everywhere, so much so that people wear sweaters indoors in the height of summer. Even waiting at a bus stop, you are misted by overhead sprinklers. So I can well imagine that people at an outdoor concert would not be at all used to actually being outside in the unmoderated heat.