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as extreme heat (FEMA, 1993). Humid conditions, which add <br /> to the discomfort of high temperatures, occur when an area of <br /> high atmospheric pressure traps hazy, damp air near the <br /> ground. <br /> Human bodies dissipate heat in one of three ways: by varying <br /> the rate and depth of blood circulation; by losing water through <br /> the skin and sweat glands; and by panting. As the blood is <br /> heated to above 98.60, the heart begins to pump more blood, <br /> blood vessels dilate to accommodate the increased flow, and <br /> the bundles of tiny capillaries penetrating through the upper <br /> layers of skin are put into operation. The body's blood is <br /> circulated closer to the surface, and excess heat is released <br /> into the cooler atmosphere. At the same time, water diffuses <br /> through the skin as perspiration. The skin handles about 90% <br /> of the body's heat dissipating function. <br /> Heat disorders generally have to do with a reduction or <br /> collapse of the body's ability to cool itself by circulatory <br /> changes and sweating, or a chemical (salt) imbalance caused <br /> by too much sweating. When the body cannot cool itself, or <br /> when it cannot compensate for fluids and salt lost through <br /> perspiration, the temperature of the body's inner core begins to <br /> rise and heat-related illness may develop. Studies indicate <br /> that, other things being equal, the severity of heat disorders <br /> tend to increase with age. Heat cramps in a 17-year old may <br /> be heat exhaustion in a 40-year old, and heat stroke in a <br /> person over 60. <br /> When the temperature gets extremely high, the NWS has <br /> increased its efforts to alert the general public as well as the <br /> appropriate authorities by issuing special weather statements. <br /> Residents should heed these warnings to prevent heat-related <br /> medical complications. As a result of the latest research <br /> findings, the NWS has devised the "Heat Index" (HI). The HI, <br /> given in degrees Fahrenheit, is an accurate measure of how <br /> hot it really feels when relative humidity is added to the actual <br /> air temperature. The NWS will initiate alert procedures when <br /> the HI is expected to exceed 105°F for at least two consecutive <br /> days. Possible heat disorders related to the corresponding HI <br /> are listed below. <br /> • Heat Index of 130°F or higher— Heatstroke/sunstroke with <br /> exposure for people in higher risk groups; <br /> Indian River County Comprehensive Emergency Management Plan Basic Page 39 <br />