A recent study has found that the frequency of extreme humid heat has more than doubled in some regions since 1979. With wet bulb temperatures rising over 35 °C, the human body can no longer effectively adapt to the heat through sweating and shedding heat through evaporation. Therefore, such extreme conditions exceed the limits of human survivability and prolonged exposure to these high temperatures in combination with high humidity are known to be deadly, even to humans with perfect health in ideal conditions.
Even in more Northern cities such as NYC, already facing high temperatures especially in summer, these effects will worsen the outside human comfort for its inhabitants even more (image below). With these extreme situations already being observed and at a predicted higher frequency in the years to come, preparing and adapting cities in advance is becoming more a matter of life and death rather than a matter of comfort.