ST. LOUIS — On a hot summer day we often hear the word dew point being used. What is dew point? It is the measure of the moisture in the atmosphere, usually near the surface, scientifically it is the temperature to which air mush be cooled to reach saturation.

Summer Dew Points — Chart from the National Weather Service

According to the National Weather Service dew point is a direct indication of how muggy (or dry) it feels outside. It is the key into deriving the heat index which is the apparent temperature “feel” on the body.

“Sweat is one of the main ways the body cools itself. But on a humid day, sweat has a harder time evaporating in the air. In high humidity, the air is already near full of water vapor and can’t hold any more” says Dr. Marny Benjamin from Health Partners.

Higher dew points mean there is more moisture in the air and the muggier it will feel. The lower the dew point means the air is drier and more comfortable.