Add Yahoo as a preferred source to see more of our stories on Google. "It's not the heat, it's the humidity." Actually, it's both, and that's where the National Weather Service's heat index comes in.

The heat index, or apparent temperature, combines air temperature and humidity to indicate how hot it feels to the body. High humidity slows sweating, the body's natural cooling system, making ...

Each week, our meteorologists answer a question from readers.

What does the "heat index" mean and how does it apply to people? -- S.S., Tulsa. The World Almanac and Book of Facts, updated annually, always includes the heat index ...

Heat advisories have been issued for various parts of Florida, urging residents to take precautions. Dangerous heat is expected on Florida's Treasure Coast, with predicted heat index values from 109 ...

Florida is under a heat advisory with dangerous heat index values expected to reach 110-115 degrees. This heat wave coincides with the one-year anniversary of the hottest day on record for Earth. The ...

Conditions are hot and humid in Michigan and getting hotter as the week goes on. Forecasters often refer to the heat index as a way to measure the "feels like" temperature. Here's a look at what that ...