Until now, it had been assumed that a wet-bulb temperature of 95°F (35°C), equivalent to 95°F at 100 percent humidity or 115°F at 50 percent humidity, marked the upper safety limit for humans.

In 2010, researchers came up with a theoretical wet bulb limit of 35 degrees Celsius, or 95 degrees Fahrenheit, at 100% humidity. This is the theoretical humid heat limit for humans.