We all know what temperatures are but in the summer when it’s hot, what exactly does that higher number that they call a head index mean?

Kurt Kotenberg with the National Weather Service explains just why this number exists.

“Basically what the human body does when it gets really hot is it tries to sweat and so the sweat is the way of the body to try and release the heat.  When there’s a lot of humidity there’s less room in the air for the sweat bubbles, if you will, to kind of evaporate off of your skin and go into the air, which cools you down.  So those sweat bubbles are more or less trapped on your skin, which is why when it’s more humid out typically you kind of just feel hotter and it feels warmer to the human body.”

When the heat index gets to be at least 105 degrees for more than three hours per day for two consecutive days, or is greater than 115 degrees for any period of time, the National Weather Service will issue an Excessive Heat Warning.

Heat advisories are issued when the heat index is at least 105 degrees for less than three hours per day or the nighttime low temperatures are above 80 degrees for two days.