Sometimes the obvious needs to be stated:
And what's obvious to some is not obvious to others.
Well that's obvious. 
In some instances though, the fact that a sign has to be put up, itself suggests it could still be ignored.
Yeah----"Don't ignore the warning signs", yet we double down and do, much to our regret.
Any recent examples that come to mind? :whistle:
Well, a yearly example occurs in my neck of the woods, where a handful of people die each summer do to dehydration, due to intense desert heat and having ignored the posted warnings about this heat. To begin with, we grow up being taught the importance of reading instructions, labels, and the like, a lesson that we ignore, and, then, we ignore warning signs as if they do not apply to us, but others. So, ignoring the lesson and then ignoring warning signs, people venture forth on a four mile desert hike, where the temperature demands that one drink a gallon of water per hour during hiking in order to avert dehydration, with 12 to 16 oz.of water. It sometimes ends badly.
It's a very good point you make. There is common sense (which everyone believes they have), and then there is over confidence.
Who knew you need a gallon an hour? That changes the calculus substantially.
I would suppose that even some people who read that recommendation, will ignore it because it's not convenient.
The gallon per hour rate was mentioned by a so-called expert when talking about 120 degree, high humidity, extreme conditions in the desert. But you would have to be a bit nutty to hike in said conditions, and carrying 2 gallons of water in those conditions might kill you. People who are used to working in such extreme conditions have adapted and do not require as much water as a novice. Yet there are people who have never hiked in 100+ degree conditions who do set out with very little water and die from lack of hydration. I've lived in the desert for 40 years, and I need very little water because I'm special now, like a lizard.:dry:
Isamorph
There is a huge difference between physical exertion in 107 degree heat in the shade,and 107 degree work in the sun. Similarly, each degree above 107 kicked my butt exponentially!!!!!
I think you're spot on with the "exponentially" notion, which reminds of the richter scale for earthquakes, where one click jump indicates a 10x increase in magnitude. I've no data for it, but from personal subjective experience, 115 degrees feels 30 degrees hotter than 105 degrees, and that is why I often behave as a shade seeking varmint during the summer.B)