In the hottest parts of the world, high temperatures and humidity will, for longer stretches, surpass a threshold that even young and healthy people could struggle to survive as the planet warms, study says

The paper is here

Figure 1 shows the locations:

Annual hot-hours under (A) 1.5, (B) 2, (C) 3, and (D) 4 °C of warming relative to preindustrial level