In Iran it was 115 degrees Fahrenheit today (46 C). Add in humidity and the heat index was a stunning 165 F (74 C). But what they really should be concerned about is the wet bulb reading…

A Limit to Human Heat Endurance

Thirty five degrees Celsius. According to recent research, it’s the wet bulb temperature at which the human body is rendered physically unable to cool itself in the shade. At which evaporation not longer cools the skin. A temperature that results in hyperthermia, heat exhaustion and heat stroke — even when sitting still and out of direct sunlight over the course of about 1-3 hours. Basically, it’s the physical limits of human heat endurance.

The primary factors involved in determining wet bulb temperature are atmospheric temperature and humidity. The temperature of an air parcel cooled to saturation (100 percent humidity). Basically, it’s the…