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Good Question: What Exactly Is The Heat Index?

MINNEAPOLIS (WCCO) -- The temperature on Thursday is expected to be in the mid-90s, but it could feel as hot as 110 degrees in some parts of Minnesota.

Some people call the "heat index" the summer's version of "wind chill."

"A little bit, yeah, because we always talk about the feel factor," says WCCO Chief Meteorologist Chris Shaffer. "Wind isn't involved per se, but it's a similar effect on how we feel versus looking at the thermometer."

The National Weather Service defines heat index as how hot it really feels when relative humidity is factored in with the actual air temperature. The formula is complex and most meteorologists use charts or computers to calculate it.

A forecasted heat index of 110 degrees is what it is expected to feel like in the shade. In the sun, it could feel closer to 120 degrees, depending on the number of clouds.

A heat index between 103 degrees and 125 degrees could likely lead to heat exhaustion and muscle cramps, according to the National Weather Service. That is because weather that hot affects the human body's abilities to evaporate sweat.

"The more humid the air, the tougher it is for that evaporation to occur," Shaffer said. "People always assume it's the sweat that's cooling your body, but it's really the energy that's released that gives you that cooling sensation."

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