What is the Heat Index? - WDAM-TV 7-News, Weather, Sports-Hattiesburg, MS

What is the Heat Index?


Heat Index, you hear it all the time in weather forecasts, but what exactly is it? We all have a basic idea, but do you know what it actually measures and why it's important?

To answer these questions you have to know why it was invented.

"Heat index was created to help measure the degree heat stress on humans that can occur with the combination of high temperatures and high humidity," said Daniel Lamb of the National Weather Service in Jackson.

And that combination of heat and humidity plays an important role on how well your body's cooling system works.

Your body cools down through a process called 'evaporative cooling.' Your body becomes wet as you sweat. Then wind evaporates that water, which cools your body down.

Because of the humidity in the Southeast, sweat does not get a chance to evaporate into the atmosphere as it would in less humid areas. Since that sweat can't evaporate, your body doesn't cool down as much and it makes it feel hotter than it really is.

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