National Oceanic and Atmospheric Administration Heat and humidity can be deadly combination Hot, humid weather is more uncomfortable than hot, dry weather because high humidity slows the evaporation of sweat.
Evaporation is nature's way of cooling.
Hot, humid weather is not only uncomfortable, it's dangerous to those exercising in it. For example, if the temperature is 95 and the relative humidity is 50 percent, find 95 in the temperature column on the left side, follow that row to the right to the 50 percent humidity column. The apparent temperature is 107. The colors on the chart show the level of danger of various combinations. To see what these mean, go to the heat stress index.