I’ve been in 52 C heat (125 F) and it’s no joke, but you can still walk around, even in the sun, without exerting yourself too much.
I’ve also been in a room at 70 C (almost 160 F) for a few minutes and that was terrifying. The air is as if burning your insides, it’s absolutely unbearable. There is a world of difference between these two. I image 60 C for four hours would start killing people, particularly the elderly.
















Humidity plays a big role. You can still cool down at 52 C if the air isn’t very humid (that is, when the wet bulb temperature is low enough). Wet bulb temperature is a particularly useful metric because it incorporates evaporative cooling in it. Sadly most thermometers can’t measure it.