The human heat limit
Where heat passes what a body can survive, and how we know.
Updated:
Wet bulb temperature has a ceiling. Past it, a body gains heat faster than sweat can shed it, no matter how healthy the person or how deep the shade. HeatCue’s scale ends there, at the band called Limit.
The textbook ceiling of 35 °C (95 °F)
In 2010, researchers worked out the physics for an idealized person. Young, healthy, resting in deep shade, wind on wet skin, water without end. Even that person overheats once wet bulb passes 35 °C (95 °F). The air is simply too hot and too humid to take the heat away.
What real bodies showed
A decade later, researchers put healthy young adults in climate chambers and raised the heat slowly while they did light tasks. Core temperature began climbing without relief near a wet bulb of 31 °C (88 °F), well short of the textbook number. Age and health bring the line lower still.
Where HeatCue draws the line
Limit begins at 31 °C (88 °F), the number measured on real people. When the wet bulb where you are reaches it, the verdict stops grading the heat and says the plain thing: past this line, staying cool takes cooled air, not toughness.
Conditions this severe are still rare, and the bands ask you to act long before them. Alerts fire from your own threshold up, so a Limit day never arrives unannounced.
HeatCue shows conditions and general guidance. It is an awareness tool, not medical advice.