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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 />