(Cleveland) - We've been forecasted to have another heat index value of over 100 degrees Thursday, but do you know what that means?
It combines air temperature and relative humidity to determine the human-perceived equivalent temperature—how hot it feels. For example, when the temperature is 90 °F with very high humidity, the heat index can be about 105 °F.
The human body normally cools itself by perspiration, or sweating. Heat is removed from the body by evaporation of that sweat. However, relative humidity reduces the evaporation rate because the higher vapor content of the surrounding air does not allow the maximum amount of evaporation from the body to occur.
This results in a lower rate of heat removal from the body, hence the sensation of being overheated.
Priscilla Smith, of the American Red Cross says working in the sun makes it much worse. Smith says excessive heat has caused more deaths than all other weather events in recent years.
If you are required to be outdoors, Smith says might want to watch for heat cramps and heat exhaustion.
She says there is also heat stroke, which is when a person's body is unable to cool itself. It can be a life-threatening condition.
Smith recommends people drink water, eat small meals and eat more often, and wear loose-fitting, lightweight clothing.
Get breaking news sent to your mobile phone. Text "news" to 21095.
(Copyright © 2013 by Clear Channel, all rights reserved. Photo by Getty Images.)