SECTION 4: RISK ASSESSMENT
4.5.4 Extreme Heat
Hazard Background Per information provided by FEMA, in most of the United States extreme heat is defined as a long period (2 to 3 days) of high heat and humidity with temperatures above 90 degrees. In extreme heat, evaporation is slowed and the body must work extra hard to maintain a normal temperature, which can lead to death by overwork of the body. Extreme heat often results in the highest annual number of deaths among all weather-related disasters. Per Ready.gov: • Extreme heat can occur quickly and without warning • Older adults, children, and sick or overweight individuals are at greater risk from extreme heat • Humidity increases the feeling of heat as measured by heat index Ambient air temperature is one component of heat conditions, with relative humidity being the other. The relationship of these factors creates what is known as the apparent temperature. The Heat Index Chart in Figure 4.9 uses both of these factors to produce a guide for the apparent temperature or relative intensity of heat conditions. Figure 4.9 – Heat Index Chart
Source: National Weather Service (NWS) http://www.nws.noaa.gov/os/heat/heat_index.shtml Note: Exposure to direct sun can increase Heat Index values by as much as 15°F. The shaded zone above 105°F corresponds to a heat index that may cause increasingly severe heat disorders with continued exposure and/or physical activity.
During these conditions, the human body has difficulties cooling through the normal method of the evaporation of perspiration. Health risks rise when a person is over exposed to heat. The most dangerous place to be during an extreme heat incident is in a permanent home, with little or no air conditioning. Those at greatest risk for heat-related illness include people 65 years of age and older, young children, people with chronic health problems such as heart disease, people who are obese, people who are socially isolated, and people who are on certain medications, such as tranquilizers, antidepressants, sleeping pills, or drugs for Parkinson’s disease . However, even young and healthy
Wake County Multi-Jurisdictional Hazard Mitigation Plan 2019
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