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. Historically, from 1979-2003, excessive heat exposure caused 8,015 deaths in the United States. In recent years, excessive heat has caused more deaths than all other weather related events.

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. The chart also indicates the likelihood for heat disorders, especially with prolonged exposure or strenuous activity. Excessive heat advisories and warnings are issued based on heat index values. Heat advisories are initiated when the heat index is expected to exceed 105-110°F (on the table) for at least two consecutive days. [Note: The heat index values are determined for shady, light wind conditions. Exposure to full sunshine can increase the heat index by as much as 15°F. Conditions with strong, hot, dry winds can also increase the hazard.]

In extreme heat and high humidity situations, normal evaporation is slowed and the body must work extra hard to maintain a normal temperature. As a result, life threatening heat-related illnesses can occur, sometimes leading to death. Heat-related illnesses and deaths are preventable. Knowing who is at greatest risk and preventive actions to be taken can help to prevent these life-threatening situations. Most cases occur in individuals that have been overexposed to heat or have over-exercised for their age or physical condition. Young children, the elderly and individuals with chronic illnesses or obesity are at highest risk, but even young and healthy individuals can succumb to heat if they participate in strenuous physical activities during hot weather. Animals can also suffer heat-related illnesses, which can also be life threatening.

The following factsheets will help you prepare your family, home and farm, animals, and business in efforts to minimize the impact of extreme heat situations.