Apparently 95f or 35c is the "limit" for humans - where many people will have health issues if they can't cool off otherwise.
https://en.wikipedia.org/wiki/Wet-bulb_temperature
> The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is a wet-bulb temperature of 35 °C
https://en.wikipedia.org/wiki/Wet-bulb_temperature
> The theoretical limit to human survival for more than a few hours in the shade, even with unlimited water, is a wet-bulb temperature of 35 °C