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Heat wave |
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July 2004
Produced by the National Disaster Education Coalition, Washington, D. C.
(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.)
Heat (Heat Wave)
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, more
than
700 people died 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 (see How to Recognize and Treat Heat Exhaustion and Heatstroke)
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 (see How to Recognize and Treat Heat Exhaustion and Heatstroke)
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) (see How to Recognize and Treat Heat
Exhaustion
and Heatstroke) 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.
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.
How can I protect myself in a heat wave?
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.
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.
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:
• Excessive Heat WATCH means conditions are favorable for an event
to meet or exceed
local excessive heat warning criteria in the
next 12 to 48 hours. .
• Excessive Heat WARNING means that heat values are forecast to
meet or exceed
locally
defined warning criteria for at least two days.
• Excessive Heat ADVISORY means hazardous heat conditions have
begun or will begin within 36 hours and, if caution is not exercised,
they could
become life threatening.
If you are at risk from excessive heat, you should:
• Discuss with members of your household the precautions they should take to stay
safe
in excessive heat. Everyone should know what to do
in the places where they spend time. Some places may not be air conditioned or
safe during a heat wave,
so plan alternatives.
• If your home does not have air conditioning, choose other places you could go
to get relief from the heat during the warmest part of the day.
Schools, libraries, theaters, and other community facilities often provide air-conditioned
refuge
on the hottest days. See if your area designates
cooling centers. Air conditioning
provides
the safest escape from excessive heat. During the 1995 Midwest heat wave, most
deaths happened
to people who were not in air conditioned places.
• Plan how you can change daily activities to avoid strenuous work during the Watch,
Warning, Advisory
• Discuss with a physician any concerns about members of the household who are
taking
medications or have medical conditions that may
cause poor blood circulation or reduced ability to tolerate heat. A physician
can advise you about temporary changes to medication or
other activities that
can relieve the effects
of heat.
• Plan to check on family, friends, and neighbors who do not have air conditioning
or
who spend much of their time alone. Elderly persons who
live alone or with
a working relative might need assistance on hot days. The majority of people
who
died because of the 1995 Midwest heat
wave were persons who were alone.
• Plan to wear lightweight, light-colored clothing. Light colors will reflect away
the sun's rays more than dark colors, which absorb the sun's rays.
• Get training. Take an American Red Cross first aid course to learn how to treat
heat emergencies and other emergencies. Everyone should
know how to respond,
because the effects of heat can happen very quickly.
• Ensure that your animals’ needs for water and shade are met. Bring companion
animals into cooler areas.
What to Do During a Heat Wave
• Listen to NOAA Weather Radio or local radio or television stations for up-to-date
information.
• Never leave children or pets alone in closed vehicles. Temperatures inside a
closed vehicle can reach more than 140°F (60° C) within minutes.
Exposure
to
such high temperatures can kill in minutes. Even on days that feel pleasantly
warm outside, temperatures in a closed vehicle can raise
high enough to kill
children
and pets.
• Slow down. Avoid strenuous activity. Reduce, eliminate, or reschedule strenuous
activities. High-risk individuals should stay in cool places.
Get plenty of rest
to allow
your natural "cooling system" to work. If you must do strenuous activity,
do it during the coolest part of the day, which
is usually in the early morning.
Many heat emergencies are experienced by people exercising or working during
the
hottest part of the
day.
• Take frequent breaks if you must work outdoors. Frequent breaks, especially in
a cool area, can help people tolerate heat better.
• Use a buddy system when working in excessive heat. Partners can keep an eye on
each
other and can assist each other when needed.
Sometimes exposure to heat
can cloud judgment, and, if you work alone, you may not notice this.
• Watch for signs of heat exhaustion and heatstroke. (See How to Recognize
and
Treat
Heat Exhaustion and Heatstroke.)
• Avoid too much sunshine. Sunburn slows the skin's ability to cool itself. The
sun will also heat the inner core of your body, resulting in
dehydration. Use
a sunscreen
lotion with a high sun-protection factor (SPF) rating.
• Postpone outdoor games and activities. Excessive heat can threaten the health
of athletes, staff, and spectators of outdoor games and activities.
• Avoid extreme temperature changes. A cold or even a cool shower taken immediately
after
coming indoors from hot temperatures can result
in hypothermia, particularly
for elderly and very young people.
• Stay indoors as much as possible. If air conditioning is not available, stay
on the lowest floor, out of the sunshine. Even in the warmest weather,
staying
indoors,
out of sunshine, is safer than long periods of exposure to the sun.
• Keep heat outside and cool air inside. Close any registers that may allow heat
inside. Install temporary reflectors, such as aluminum
foil-covered cardboard,
in windows
and skylights to reflect heat back outside.
• Conserve electricity not needed to keep you cool. During periods of excessive
heat, people tend to use a lot more power for air conditioning.
Conserve electricity
not used to keep you cool so power can remain available and reduce the chance
of a community-wide outage.
• Vacuum air conditioner filters weekly during periods of high use. Air conditioner
filters
can become clogged or filled with dirt, making them
less efficient. Keeping
them clean will allow your air conditioner to provide more cool air.
• If your home does not have air conditioning, go to a public building with air
conditioning
each day for several hours. Air conditioned
locations are the safest places during excessive heat because electric fans do
not cool the air. Fans
do help sweat evaporate, which gives a
cooling effect. However, when temperatures
exceed
90o F (32 o C), fans become ineffective in reducing heat-related illness.
• Dress appropriately:
-Wear loose-fitting, lightweight, light-colored clothing that will cover as much
skin as possible. Lightweight, light-colored clothing reflects
heat and sunlight
and helps maintain normal body temperature. Cover as much skin as possible to
avoid
sunburn and the over-warming effects
of sunlight on your body.
-Protect your face and head by wearing a wide-brimmed hat. A hat will keep direct
sunlight off your head and face. Sunlight can burn and warm
the inner
core of your body.
• Drink plenty of fluids even if you do not feel thirsty. Drink regularly and often.
Your body needs water to keep cool. Water is the safest liquid
to drink during
heat emergencies. Injury and death can occur from dehydration, which can happen
quickly and be unnoticed until too late.
Symptoms of dehydration are often confused
with symptoms of other conditions.
• People who have epilepsy or heart, kidney, or liver disease; who are on fluid
restricted
diets;
or who have a problem with fluid retention should
consult a doctor before increasing liquid intake.
• Avoid drinks with alcohol or caffeine. They can make you feel good for a little
while, but they make the heat's effects on your body worse.
This is especially
true
about beer, which actually dehydrates the body.
• Eat small meals and eat more often. Large, heavy meals are more difficult to
digest and cause your body to increase internal heat to aid digestion,
worsening
overall conditions. Avoid foods that are high in protein, such as meats and nuts,
which
increase metabolic heat.
• Avoid using salt tablets unless directed to do so by a physician. Salt causes
the body to retain fluids, resulting in swelling. Salt impedes sweating,
which
helps
keep you cool.
• Check on your animals frequently to ensure that they are not suffering stress
from the heat. Make sure they are indoors or in the shade. Use fans
to cool areas
that
are not air conditioned or open to breezes. Provide plenty of water for drinking
as well
as for cooling the animals. If you see signs
of heat stress, call your veterinarian.
Very young
and older animals, as well as animals with short snouts, are more susceptible
to problems
with heat.
How to Make Your Home Safer for Occupants in a Heat Wave
• Install window air conditioners snugly. Insulate spaces around air conditioners
for a tighter fit. An air conditioner with a tight fit around
the windows or
wall
openings
will make less noise and allow less hot air in from the outside.
• Make sure your home is properly insulated. This will help you to conserve electricity
and
reduce your home's power demands for air
conditioning. Put weather stripping around doors and windows to keep cool air
inside.
• Consider keeping storm windows installed throughout the year. Storm windows can
keep the heat out of a house in the summer the
same way they keep the cold out
in
the winter.
• Check air-conditioning ducts for proper insulation. Insulation around ducts prevents
cool
air from leaking and keeps it directed through the vents.
• Protect windows from the sun. Hang shades, draperies, awnings, or louvers on
windows
receiving morning or afternoon sun. Outdoor
awnings or louvers can reduce
the heat entering the house by as much as 80 percent.
• Use an attic fan. If you have a fan installed to vent warm air out of your attic,
use it to help keep your home cool.
• Check buildings that house animals.
How to Recognize and Treat Heat Exhaustion and Heatstroke
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.
Heat Exhaustion
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
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, ask 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.
Media and Community Education Ideas
• Ask your local newspaper or radio or television station to:
-Do a series with
information about excessive heat emergencies. Help the reporters
to localize the information by providing the telephone numbers
of local emergency
services offices, the local American Red Cross chapter, and nearby hospitals.
-Do a story featuring interviews with local physicians about the dangers of sunburn,
heat exhaustion, heatstroke, and other conditions caused
by excessive heat.
-During a drought, run a series suggesting ways individuals can conserve water
and energy in their homes and their workplaces.
-Interview local officials and representatives of the U.S. Department of Agriculture
about special steps farmers can take to establish alternative
water supplies
for
their
crops and ways to protect livestock and poultry from the effects of excessive
heat.
• Sponsor a "Helping Your Neighbors" program through your local school
system to encourage children to think of how they can help people who
require
special assistance during severe weather conditions, such as elderly people,
infants,
or people
with disabilities.
• Arrange for air-conditioned shelters to be opened when necessary for community
members
who do not have air conditioning at home.
• Arrange for special programs to provide air conditioners to vulnerable people
in their homes.
Facts and Fiction
Fiction: Beer and other alcoholic beverages satisfy thirst in excessive heat.
Fact: 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.
Fact: 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.
Fact: 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.
Fact: 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.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.
To protect yourself:
- Limit time in the midday sun.
- Stay in shade.
- Use a broad-spectrum sunscreen of at least SPF15+ and reapply it every two
hours.
- Wear a hat, protective clothing, and sunglasses.
- Watch for the UV Index (reported in local news and newspapers).
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