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 ...

Extreme heat makes it especially hard for your body to cool down, so you need to be extra careful if you exercise or play ...

Hundreds of people working or playing outside – even those who seem healthy – succumb to heat-related illnesses each year.

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 ...