The temperature on any given summer day may be in the 80s or 90s. So why does it feel so much hotter and oppressive at times? That's the heat index doing its thing. Here's how it works: What is the ...

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.

If you thought the worst of the summer's sweltering temperatures were behind us, think again. Some schools closed early as the late-August heat wave gripping Ohio brought temperatures not seen in ...

"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 ...