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Learn what heat hazards may occur where you are and how to plan for excessive heat should it occur in your area. Different areas have different risks associated with prolonged heat. Contact your local emergency management office, National Weather Service office, or American Red Cross chapter for information.
(Review acknowledgment: The Environmental Protection Agency, Office of Atmospheric Programs, Global Programs Division, Global Change Information Branch, reviewed this chapter, in addition to the agencies listed in the acknowledgments and on the cover of Talking About Disaster: Guide for Standard Messages.)
Why talk about excessive heat?
In recent years, excessive heat has caused more deaths than all other weather events, including floods. The American meteorological Society reports that on average heat kills more than 1,000 people each year. During the July 1995 heat wave in Chicago, approximately 525 people died over a 5-day period. Thousands of people were taken to local hospitals as a result of excessive heat.
What is a heat wave?
A heat wave is a prolonged period of excessive heat, often combined with excessive humidity. Generally, excessive heat is defined as temperatures that hover 10 degrees or more above the average high temperature for the region during summer months, last for a prolonged period of time, and often are accompanied by high humidity.
What is the heat index?
The heat index is the temperature the body feels when the effects of heat and humidity are combined. Exposure to direct sunlight can increase the heat index by up to 15°F.
What are heat cramps, heat exhaustion, heatstroke, and sunstroke?
Heat cramps are muscular pains and spasms caused by heavy exertion in high heat. Heat cramps are often the first sign that the body is having trouble with the heat. Heat exhaustion typically involves the loss of body fluids through heavy sweating when someone strenuously exercises or works in high heat and humidity. In someone suffering from heat exhaustion, blood flow to the skin increases while blood flow to vital organs decreases, resulting in a mild form of shock. If not treated, body temperature will continue to rise and the person may suffer heatstroke.
Heatstroke (also known as sunstroke) is a life-threatening condition in which a person's temperature control system, which produces sweating to cool the body, stops working. The body temperature of someone suffering from heatstroke can rise so high that brain damage and death may result if the body is not cooled quickly.
How can I protect myself in a heat wave?
The best ways to be protected from the ill effects of excessive heat are to dress appropriately, stay indoors, refrain from strenuous work or exercise during the hottest part of the day, and stay hydrated. Spending at least two hours a day in air conditioning significantly decreases a person's risk of heat-related illnesses.
Heat can kill by pushing the human body beyond its limits. Under normal conditions, the body's internal thermostat produces perspiration that evaporates and cools the body. However, in excessive heat and high humidity, evaporation is slowed and the body must work extra hard to maintain a normal temperature.
Elderly people, young children, and those who are sick or overweight are more likely to become victims of excessive heat. Because men sweat more than women do, they become more quickly dehydrated and are more susceptible to heat illness.
The duration of excessive heat plays an important role in how people are affected by a heat wave. Studies have shown a significant rise in heat-related illnesses when excessive heat lasts more than two days.
People living in urban areas may be at greater risk from the effects of a prolonged heat wave than are people living in rural regions. An increased health problem, especially for those with respiratory difficulties, can occur when stagnant atmospheric conditions trap pollutants in urban areas, thus adding unhealthy air to excessively hot temperatures. In addition, asphalt and concrete store heat longer and gradually release heat, resulting in significantly higher temperatures, especially at night -- an occurrence known as the "urban heat island effect."
Pets, horses, and livestock are also susceptible to difficulties from excessive heat. Animals do not perspire and rely on panting, wetting down, shade, cool earth, and drinking water for cooling. Animals cannot explain their needs, so it is up to people to take extra care that during heat waves, their needs are met.
What is the best source of information in a heat wave?
Local radio, television stations, and NOAA Weather Radio are the best sources of information in a heat wave.
NOAA Weather Radio is the prime alerting and critical information delivery system of the National Weather Service (NWS). NOAA Weather Radio broadcasts warnings, watches, forecasts, and other hazard information 24 hours a day over more than 650 stations in the 50 states, adjacent coastal waters, Puerto Rico, the U.S. Virgin Islands, and the U.S. Pacific territories.
The NWS encourages people to buy a weather radio equipped with the Specific Area Message
Encoder (SAME) feature. This feature automatically alerts you when important excessive heat
information is issued for your area. Information on NOAA Weather Radio is available from your
local NWS office or at www.nws.noaa.gov/nwr.
Watch, Warning, Advisory
The National Weather Service issues alerts for excessive heat on a county-by-county basis. The alerts are broadcast on NOAA Weather Radio and on local radio and television stations. The parameters of an excessive heat watch, warning, and advisory vary by location. Generally:
Be Prepared for a Heat Wave Protect Yourself
For general preparedness, every household should create and practice a Family Disaster Plan and assemble and maintain a Disaster Supplies Kit. In addition, households at risk from heat waves should take precautions to stay safe in case one occurs. Review your Family Disaster Plan before summer heat is expected and be sure to stock additional water.
If you are at risk from excessive heat, you should:
What to Do During a Heat Wave
During a heat wave, you should:
How to Make Your Home Safer for Occupants in a Heat Wave
To make your home safer during a heat wave, you should:
How to Recognize and Treat Heat Exhaustion and Heatstroke
The signs of heatstroke in a person are hot, red skin; changes in consciousness; rapid, weak pulse; and rapid, shallow breathing. A person experiencing heatstroke can have a very high body temperature -- sometimes as high as 105°F (41° C). If the person was sweating from heavy work or exercise, the skin may be wet; otherwise, it will feel dry.
Heatstroke is a life-threatening situation. If you suspect someone is suffering from heatstroke, call 9-1-1 or your local emergency number immediately. Move the person to a cooler place. Quickly cool the person's body -- immerse it in a cool bath or wrap it in wet sheets and fan it. Watch for signs of breathing problems. Keep the person lying down and continue to cool the body any way you can. If the person refuses water, is vomiting, or exhibits changes in the level of consciousness, do not give him or her anything to eat or drink.
Do not give liquids that contain alcohol or caffeine because they can cause further
dehydration, making conditions worse.
The signs of heat exhaustion in a person are cool, moist, pale, or flushed skin; heavy sweating; headache; nausea or vomiting; dizziness; and exhaustion. A person experiencing heat exhaustion may have a normal body temperature, or it is likely to be rising.
If you suspect someone is suffering from heat exhaustion, move the person to a cooler place. Remove or loosen tight clothing and apply cool, wet cloths, such as towels or sheets dipped in water. If the person is conscious, give him or her cool water to drink. Make sure the person drinks slowly. Give a half glass of cool water every 15 minutes. Let the person rest in a comfortable position, and watch carefully for changes in his or her condition.
Do not give liquids that contain alcohol or caffeine because they can cause further dehydration, making conditions worse.
Heat cramps are muscle spasms that are caused by excessive sweating that results in a deficiency of salt. Although not as serious as heat exhaustion or heatstroke, heat cramps sometimes precede them. If someone is suffering from heat cramps, move the person to a cooler place and have him or her rest in a comfortable position. Lightly stretch the affected muscle and replenish fluids. Give a half glass of cool water every 15 minutes.
Do not give liquids that contain alcohol or caffeine because they can cause further dehydration, making conditions worse.
Heat Stroke in Animals
Animals are also susceptible to heat stroke, or hyperthermia, which is considered an emergency as it is with people. Signs in animals include excessive panting; increased body temperature, heart rate, or respiratory rate; unusual salivation; collapse, stupor, seizures, or coma; redder than normal mucous membrane (gums, for example); or capillary refill that is too fast. Be aware also of signs of dehydration, which is also an emergency. For more information about first aid for cats and dogs, refer to Pet First Aid, by Barbara Mammato, DVM, MPH, a handbook sponsored by the American Red Cross and The Humane Society of the United States. For information about other animals, talk with your veterinarian.
If you suspect heat stroke, get the animal out of direct heat and spray it with cool water or place water-soaked towels on its head, neck, feet, chest, and abdomen. The consequences of heat stroke may be life-threatening, but might not be visible to you for several hours, so take the animal to your nearest veterinary hospital right away.
Facts and Fiction
Fiction: Beer and other alcoholic beverages satisfy thirst in excessive heat.
Facts: Although beer and alcoholic beverages appear to satisfy thirst, they actually cause further body dehydration. You should limit your intake of alcoholic beverages in excessive heat. Drink plenty of water. Your body needs water to keep cool. Drink plenty of fluids even if you do not feel thirsty. (People who have epilepsy or heart, kidney, or liver disease; are on fluid restricted diets; or have a problem with fluid retention should consult a physician before increasing their consumption of fluids.)
Fiction: It's always good to exercise, no matter how hot it is.
Facts: Many heat emergencies are experienced by people exercising or working during the hottest parts of the day. Reduce, eliminate, or reschedule strenuous activities. If you must do strenuous activity, do it during the coolest part of the day which is usually in the morning between 4:00 a.m. and 7:00 a.m.
Fiction: A heatstroke (sunstroke) is not life-threatening.
Facts: A heatstroke or sunstroke is life threatening. If someone has heatstroke, his or her temperature control system, which produces sweat to cool the body, stops working. The body temperature can rise so high that brain damage and death may result if the body is not cooled quickly.
Fiction: You will get sunburned only on really hot days.
Facts: Sunburn (and tanning) results from exposure to ultraviolet (UV) radiation, which is distinct from the light and heat emitted by the sun. You cannot see or feel UV rays. They can, however, be quite damaging. UV exposure has been linked to skin cancer and other skin disorders, cataracts and other eye damage, and immune-system suppression. The ozone layer
absorbs most of the sun's harmful UV rays, but this layer has thinned in recent years as a result of the emission of ozone-depleting chemicals. This thinning can lead to a greater chance of overexposure to UV radiation.
To protect yourself:
Watch for the UV Index (reported in local news and newspapers) UV exposure is a year-round issue -- you can sustain damage on the ski slopes just as easily as on the beach, and clouds provide only partial protection. For more information, visit http://www.epa.gov/sunwise.
Last Updated: 6/18/2012