This looks even more alarming if you factor in humidity. Human beings can tolerate heat with sweat, which evaporates and cools the skin. That is why a dry 50°C can feel less stifling than a muggy 30°C. If the wet-bulb temperature (equivalent to that recorded by a thermometer wrapped in a moist towel) exceeds 35°C, even a fit, healthy youngster lounging naked in the shade next to a fan could die in six hours.
At present, wet-bulb temperatures seldom exceed 31°C.
The first paper I ever published was on sweating. It was my entry as a medical student into dermatology, and the product of meeting Sam Shuster (the rest, as they say, is history). Sweat glands don’t get a lot of attention, but the ~3 million mini-kidneys are full of fascinating biology. Did you know you can shift more fluid through your sweat glands that you can pass urine (quite a thought, considering how many pints of beer some people can manage — and no, I do not have a reference for this factoid so readers beware……).