The Heat Index Chart. Source: NOAA NWS. The National Weather Service Heat Index Chart is available at:

Excessive Heat

Extreme heat conditions (e.g., heat waves) can occur in most regions of the U.S. High temperatures combined with humidity can be extremely hazardous and can result in heat-related illnesses and even death.

The Heat Index Chart is used to help monitor extreme heat conditions. The heat index is the temperature the body feels when the effects of temperature and humidity are combined and indicates the likelihood for heat disorders, especially with prolonged exposure or strenuous activity. Heat advisories are initiated when the heat index is expected to exceed 105-110°F for at least two consecutive days.

Extreme heat and high humidity situations can be life threatening. Taking the necessary precautions can help to prevent this from occurring. Most cases of illness or death occur in individuals that have been overexposed to heat or have over-exercised for their age or physical condition.

Young children, the elderly, individuals with chronic illnesses or obesity are at highest risk, but even young and healthy individuals be affected if they participate in strenuous physical activities during hot weather without taking precautions. Animals can also suffer heat-related illnesses, which can also be life threatening.

The following resources will help you prepare your family, home and farm, animals and business for excessive heat situations.

Excessive Heat Web Resources

Extreme Heat
Website with tips on heat prevention, affects on elderly and what you should know about heat.
Centers for Disease Control and Prevention (CDC)
Extreme Heat
Website with information on summer safety issues, including food safety, sun exposures, insect avoidance.
Centers for Disease Control and Prevention
Heat: A Major Killer
Website of information about heat wave warnings, hazards and preventive actions.
National Weather Service (NOAA NWS) Extreme Heat
Website with extreme heat terms, as well as how to prepare for extreme heat, what to do during and after.
Federal Emergency Management Agency (FEMA)

More Excessive Heat Factsheets

Heat (Heat Wave)
Document on extreme heat emergencies, how to prepare before they occur, and treat heat-related illnesses.
National Disaster Education Coalition
Heat Stress
Factsheet discusses symptoms of heat stroke and exhaustion and the emergency procedures associated with these illnesses.
Ohio State University Extension
Protecting Yourself From Heat Stress
Information on heat stroke, heat stress, heat exhaustion, and protecting yourself from these illnesses.
Centers for Disease Control and Prevention (CDC)