The fact people already live in some of the hottest places in the world today should speak a little to human resiliency.

We can live in hot places if the air stays dry, which it usually does or historically did. If the air gets more humid we cannot anymore.

> Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above 35 °C (95 °F) for six hours.

https://en.wikipedia.org/wiki/Thermoregulation