How to cope with excessive heat

At certain levels, the human body cannot maintain proper internal temperatures and may experience heat stroke. The "Heat Index" is a measure of the effect of the combined elements on the body.

Excessive Heat Outlook

This CPC product, a combination of temperature and humidity over a certain number of days, is designed to provide an indication of areas of the country where people and animals may need to take precautions against the heat during May to November.

Excessive Heat Warning

Issued within 12 hours of the onset of the following criteria: heat index of at least 105° F for more than 3 hours per day for 2 consecutive days, or heat index more than 115° F for any period of time.

Excessive Heat Watch

Issued by the National Weather Service when heat indices in excess of 105° F (41° C) during the day combined with nighttime low temperatures of 80° F (27° C) or higher are forecast to occur for two consecutive days.

How Heat Affects the Body | Too Much Heat | Preventing Heat-Related Illnesses | Heat Wave Safety Tips | Possible Heat Disorders | First Aid | Dogs and Heat

How Heat Affects the Body

Human bodies dissipate heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and-as the last extremity is reached by panting, when blood is heated above 98.6 degrees. The heart begins to pump more blood, blood vessels dilate to accommodate the increased flow, and the bundles of tiny capillaries threading through the upper layers of skin are put into operation. The body's blood is circulated closer to the skin's surface, and excess heat drains off into the cooler atmosphere. At the same time, water diffuses through the skin as perspiration. The skin handles about 90 percent of the body's heat dissipating function.

Sweating, by itself, does nothing to cool the body, unless the water is removed by evaporation-and high relative humidity retards evaporation. The evaporation process itself works this way: the heat energy required to evaporate the sweat is extracted from the body, thereby cooling it. Under conditions of high temperature (above 90 degrees) and high relative humidity, the body is doing everything it can to maintain 98.6 degrees inside. The heart is pumping a torrent of blood through dilated circulatory vessels; the sweat glands are pouring liquid-including essential dissolved chemicals, like sodium and chloride onto the surface of the skin.

Too Much Heat

Heat disorders generally have to do with a reduction or collapse of the body's ability to shed heat by circulatory changes and sweating, or a chemical (salt) imbalance caused by too much sweating. When heat gain exceeds the level the body can remove, or when the body cannot compensate for fluids and salt lost through perspiration, the temperature of the body's inner core begins to rise and heat-related illness may develop.

Ranging in severity, heat disorders share one common feature: the individual has overexposed or overexercised for his age and physical condition in the existing thermal environment. Sunburn, with its ultraviolet radiation burns, can significantly retard the skin's ability to shed excess heat.

Studies indicate that, other things being equal, the severity of heat disorders tend to increase with age-heat cramps in a 17-year-old may be heat exhaustion in someone 40, and heat stroke in a person over 60. Acclimatization has to do with adjusting sweat-salt concentrations, among other things. The idea is to lose enough water to regulate body temperature, with the least possible chemical disturbance.

Preventing Heat-Related Illness

Elderly persons, small children, chronic invalids, those on certain medications or drugs (especially tranquilizers and anticholinergics), and persons with weight and alcohol problems are particularly susceptible to heat reactions, especially during heat waves in areas where a moderate climate usually prevails.

Heat Wave Safety Tips

  • Slow down. Strenuous activities should be reduced, eliminated, or rescheduled to the coolest time of the day. Individuals at risk should stay in the coolest available place, not necessarily indoors.
  • Dress for summer. Lightweight, light-colored clothing reflects heat and sunlight, and helps your body maintain normal temperatures.
  • Put less fuel on your inner fires. Foods (like proteins) that increase metabolic heat production also increase water loss.
  • Drink plenty of water or other non-alcohol fluids. Your body needs water to keep cool.
  • Drink plenty of fluids even if you don't feel thirsty. Persons who (1) have epilepsy or heart kidney, or liver disease, (2) are on fluid restrictive diets or (3) have a problem with fluid retention should consult a physician before increasing their consumption of fluids.
  • Do not drink alcoholic beverages.
  • Do not take salt tablets unless specified by a physician. Persons on salt restrictive diets should consult a physician before increasing their salt intake.
  • Spend more time in air-conditioned places. Air conditioning in homes and other buildings markedly reduces danger from the heat. If you cannot afford an air conditioner, spending some time each day (during hot weather) in an air conditioned environment affords some protection.
  • Don't get too much sun. Sunburn makes the job of heat dissipation that much more difficult.

Possible Heat Disorders According to Heat Index:

80 to 90 degrees - Fatigue possible with prolonged exposure and/or physical activity.
90 to 105 degrees - Sunstroke, heat cramps, and heat exhaustion possible with prolonged exposure and or physical activity.
105 to 130 degrees - Sunstroke, heat cramps or heat exhaustion likely, and heatstroke possible with prolonged exposure and/or physical activity.
130 degrees and higher - Heatstroke/sunstroke highly likely with continued exposure.

Know These Heat Disorder Symptoms


Symptoms include redness and pain, cases swelling of skin, blisters, fever, headaches.
For treatment, use ointments for mild cases if blisters appear and do not break. If breaking occurs, apply dry sterile dressing. Serious extensive cases should be seen by a physician.


Symptoms include painful spasms usually in muscles of legs and abdomen possible; also heavy sweating.
For treatment, apply firm pressure on cramping muscles, or use gentle massage to relieve spasms. Give sips of water. If nausea occurs, discontinue use.


Symptoms include heavy sweating, weakness, skin cold, pale and clammy Pulse thready. Normal temperature possible. Fainting and vomiting.
For treatment, get the victim out of sun. Lay the person down and loosen clothing. Apply cool, wet cloths and use a fan or move the victim to an air conditioned room. Give sips of water. If nausea occurs, discontinue use. If vomiting continues, seek immediate medical attention.


Symptoms include high body temperature (106F or higher), and hot dry skin. Rapid and strong pulse. Unconsciousness possible.
Move the victim to a cooler environment. Reduce body temperature with cold bath or sponging. Use extreme caution. Remove clothing, use fans and air conditioners. If temperature rises again, repeat process. Do not give fluids.

For more information, contact your local American Red Cross Chapter. Ask to enroll in a first aid course.


Dogs cannot sweat or regulate their body temperature. If your dog is not responding or their ears are feeling hot, spray them with water and take them to the vet immediately. They could be suffering from a heat stroke.

Sources: NOAA's National Weather Service, the Federal Emergency Management Agency, and the American Red Cross.

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