We hear about it often this time of year, but just what is the heat index? It’s a calculation to measure how hot it feels based on the temperature and humidity.
To figure out the heat index, you need to know what the temperature is and what the dewpoint temperature is. The dewpoint is one of the main factors meteorologists use to determine how humid the air is. The higher the dewpoint, the more muggy it feels outside.
For example, if the air temp is 95° and the dewpoint is 70°, the heat index—or what it feels like—would be 102°.
[Related: Staying Safe from Thunderstorms]
So it’s just as important to keep track of the heat index as it is the actual air temperature this time of year. Once the heat index reaches 105°, that’s considered to be dangerous.
This news clip from 2013 gives a visual demonstration: