"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. Also known as the apparent temperature, the heat index is a number ...

ANGELES. WELL, WE ALL KNOW HOW HOT IT GETS HERE DURING THE SUMMER IN SOUTH FLORIDA, BUT IT ACTUALLY FEELS MUCH HOTTER WHEN YOU FACTOR IN THE HUMIDITY. FIRST WARNING METEOROLOGIST BROOKE SILVERING ...

Add Yahoo as a preferred source to see more of our stories on Google. The sticky combination of heat and high humidity can be more than uncomfortable -- it can be deadly. Mario Tama/Getty Images ...