Heat Stress Informational Charts

Heat Index

High temps and humidity are the biggest environmental factors contributing to heat stress. These work in combination to create what is called a heat index. This is a heat index chart provided by the CDC (Center for Disease Control), which shows the perceived temperature when both air temp and humidity are considered.

You can see that the hotter the temperature, in combination with a high humidity, the more dangerous the environment becomes and the more uncomfortable it feels. Especially be aware of heat exhaustion, heat cramps or heat stroke when workers are in environments of 85 degrees F or above, which are reflected in the orange and red zones.

Heat Stress Symptoms and Treatments


View Chart

This chart outlines the four most common HRIs in order of severity.

  • Heat rash occurs when sweat ducts become clogged and sweat can't get to the surface of the skin.
  • Heat cramps typically affect workers who sweat a lot during strenuous activity. Sweating depletes the body’s salt and moisture levels and produces painful spasms usually in the legs or abdomen.

These are the two least severe, but still should be taken seriously. Response to an individual exhibiting these signs is to get them to a cool, shaded area, apply something cool on them, and make sure they drink plenty of fluids. Monitor symptoms and seek medical attention if symptoms do not subside or get worse. The two most severe HRIs are heat exhaustion and heat stroke.

  • Heat exhaustion is a milder form of heat stroke that can develop over the course of several days of exposure to high temperatures and dehydration. The body’s response to this excessive loss of water and salt is through extreme sweating. Untreated heat exhaustion may progress to heat stroke if you do not act quickly once seeing someone exhibiting signs.
  • Heat stroke is a condition that occurs when the body becomes unable to control its temperature, and can cause death or permanent disability. Heat stroke is a true medical emergency that can be fatal if not properly and promptly treated, so it’s absolutely critical to seek medical attention immediately upon recognizing signs related to this HRI.