Bingo. Folks just don't watch their water intake, and it has to be water (The caffeine in soft drinks apparently is a mild diuretic, pretty much offsetting what you take in as water). I regularly work outside with temps in excess of 100.
Still, they should know better, especially when the humidity is high and they're sweating bullets. We don't get that kind of warning here most of the time. You don't sweat all that much when the RH is howering in the teens or less.
I think the lib-media is blowing this all out of proportion though. It looks like a pretty small percentage to me.