ItÕs summer, and in case you havenÕt noticed -- itÕs HOT! It hasnÕt rained since the 25th of last month and Monday the high temperature in Nacogdoches was 103 with a heat index of 121! My car doesn't have air conditioning, and worse yet, has only two windows that open and one of them just half way. When I first get in after itÕs been parked in the sun, the interior is only slightly cooler than the surface of the sun and even racing down the road on a day like yesterday with its one and a half windows wide open, you could still melt lead inside.
Summer heat can be more than miserable, it can kill, especially when both the humidity and temperature are high. Our body depends on a steady internal temperature of about 99 degrees in order to keep us running smoothly. A little higher or lower and we can quickly be in trouble. When the weather is hot, sensors under our skin and a central heat control unit in our brain (the hypothalamus) start our evaporative cooler running by producing perspiration that bathes us with moisture. As sweat evaporates, it cools us, keeping our bodyÕs temperature within normal limits. At low humidities, the system works quite well since evaporation is rapid, but as the humidity rises, drying isnÕt as fast and we begin to notice that it feels ÒstickyÓ and hotter. With further rises in humidity, sweat may soak our clothing and literally drip off our noses as our body tries to keep its temperature down.
The relationship between air temperature and relative humidity is call the Heat Index and is usually reported in the newspaper and on the news. The chart shown here will give you the idea. In one sense, the Heat Index is a measure of how much hotter it feels than the actual air temperature - a kind of comfort score, but it also is a hazard rating indicating how much heat stress our body is under. Any time the Heat Index reaches 90, heat exhaustion is possible. If it rises to 103, heat stroke is possible and at 130, heat stroke is imminent. Yesterday, with the index at 121, danger of serious heat illness was very high.
When the heat load on our body becomes too great, heat stroke and heat exhaustion can set in. Of the two, heat stroke is the most serious, and is sometimes called sunstroke. It is a life threatening medical emergency. Often developing suddenly, heat stroke may begin with a headache, dizziness, nausea, vomiting and extreme fatigue. The skin is hot, flushed and usually dry. Pulse rate increases and we breathe faster. Confusion, incoherent speech and aggressive behavior may become evident and the victim will often lose consciousness and may quickly pass into a coma and die. In heat stroke, the hypothalamus (remember our brainÕs thermostat?) no longer functions properly and the bodyÕs core temperature soars, exceeding 105 degrees - high enough to quickly cause brain damage in adults. Heat stroke is so serious that victims sometimes die even though they are being treated in an emergency room. If a person shows signs of heat stroke, quickly get the victim into a cool place, remove most clothing and cover them with cool towels soaked in water. If an electric fan is available, turn it on them to increase evaporative cooling or have someone manually fan the victim. Call an ambulance and get them to a hospital as quickly as possible.
Heat exhaustion, generally caused by heat combined with dehydration, is usually less serious and more gradual in its onset, but it can easily progress to full blown heat stroke. The victim is usuallyT¸€