PURDUE 2022
31°C Wet Bulb Limit
Purdue University (2022) research by Vecellio et al. established that the actual human survivability limit is approximately 31°C wet bulb for young, healthy adults at rest in shade with unlimited water. This is significantly lower than the previously theoretical 35°C limit.
THEORETICAL 35°C
35°C Wet Bulb Limit
The theoretical 35°C wet bulb limit (Sherwood & Huber 2010) assumed a perfectly sweating human in ideal conditions (shade, rest, unlimited water, no clothing). Real humans cannot survive this — the Purdue study showed heat stress becomes uncompensable at ~31°C WB.
CRITICAL >35°C
Unsurvivable Threshold
Above 35°C wet bulb, the human body cannot cool itself through sweating even under ideal conditions. Heat death is inevitable within hours regardless of age, fitness, or hydration. This threshold has been briefly exceeded in places like Jacobabad, Pakistan and Ras Al Khaimah, UAE.