Amateurs. I spent more summers than I care to recall working in steel mills. At the end of the day your clothes look like they were tie dyed. All the salt dries in white swirls. Nothing like a hot summer day while watching a river of molten metal roll by. Add hard, physical work, and you truly know discomfort. In those conditions you can die if you don't pay attention to your body. Water stations and fresh lemons and oranges keep you going.
As a result of those 25 years, I completely avoid heat when possible. And like they say, it's not the heat, it's the humidity. 90 degrees in New York is tougher than 120 degrees in the desert.