Extreme levels of heat and humidity are forecast to spread across the country over the next two weeks, blanketing the Southwest, Midwest, and East Coast with high temperatures beginning this June 19 ...

It’s a T-shirt kind of day in Washington, DC: 85 degrees with 63 percent humidity. We all know those numbers mean hot, but what exactly does that humidity percentage tell us? And why should we care?

Relative humidity and dew point both give us an idea of the amount of moisture in the atmosphere; however, only dew point is a true measurement of the atmospheric moisture. Relative humidity is ...