“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 that combines relative humidity with the air temperature. That resulting figure is the temperature it actually feels like to the human body.
➤ Weather alerts via text: Sign up to get updates about current storms and weather events by location
It’s important to note the heat index chart calculates the apparent temperature based on a shady location. In direct sunlight, the “feels-like” temperature could be up to 15 degrees higher.
Here’s what you should know about the heat index.
What is the heat index?
The heat index, also called the apparent temperature, is a measure of how hot it really feels on your body when relative humidity is factored in with the actual air temperature.
To find the heat index temperature, look at the heat index chart or check the NWS Heat Index Calculator.
For example, if the air temperature is 96°F and the relative humidity is 65%, the heat index — or how hot it feels — is 121°F. The red area without numbers indicates extreme danger.
Important reminder: Heat index calculated for shade, light wind
Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15 degrees.
Also, strong winds, particularly with very hot, dry air, can be extremely hazardous, the National Weather Service said.
How hot is too hot to exercise?
The National Weather Service said a heat index equal or greater than 103 “can lead to dangerous heat disorders with prolonged exposure and/or physical activity in the heat.”
This article originally appeared on Tallahassee Democrat: What is the heat index and how hot is too hot to exercise?
Reporting by Cheryl McCloud, USA TODAY NETWORK – Florida / Tallahassee Democrat
USA TODAY Network via Reuters Connect
