HEAT – THE NUMBER ONE NON-SEVERE
KILLER IN THE UNITED STATES
2, 2006 — The
summer of 2006 is far from over and already more than 150 people in the
United States have died as a direct result of heat.
normal temperatures are expected for much of the nation throughout
the month of August,
as has been the case in the continental U.S. for all
of 2006, according to the NOAA
National Climatic Data Center in Asheville, N.C.
Of all the
natural hazards in the United States, heat is the number one non-severe
weather related killer. Unlike the roar of an approaching tornado, heat
waves kill with silence. In an average year, about 175 Americans succumb
to the effects of summer heat, according to the NOAA
Office of Climate, Water, and Weather Services and the NOAA National
Climatic Data Center. In the 40-year period from 1936 through 1975, nearly
20,000 people were killed in the United States by the effects of heat
and solar radiation. In the disastrous heat wave of 1980, more than 1,250
people died. Through improved heat-wave forecasting, plus greater public
awareness and education, NOAA is working to help reduce the number of
Waves Can Strike Almost Anywhere in the United States
American summers are hot; most summers see heat waves in one section or
another of the United States. East of the Rockies, heat waves tend to
combine both high temperature and high humidity, although some of the
worst heat waves have been catastrophically dry (as was experienced in
California this summer).
in the northeastern and midwestern United States typically have the strongest
weather mortality relationships because weather variability, rather than
heat intensity, is the single most important factor in defining human
sensitivity to heat. People living in highly variable summer climates
are not well adapted to extreme heat, mainly because it occurs irregularly.
As a result, temperate cities like Philadelphia, Boston, Chicago and New
York exhibit extreme increases in the number of deaths reported when an
intense heat wave occurs compared to many more tropical cities. This is
one reason that early season heat waves are associated with higher mortality
— because people within the city population acclimate to the heat
as the hot season continues.
The NOAA National Weather Service Heat Index Program
NOAA National Weather Service has
stepped up its efforts to more effectively alert the general public and
appropriate authorities to the hazards of heat waves — those prolonged
excessive heat/humidity episodes.
the latest research findings, the NOAA National Weather Service has devised
Index,” (sometimes referred to as the “apparent temperature”).
The Heat Index, given in degrees Fahrenheit, is an accurate measure of
how hot it really feels when relative humidity is added to the actual
find the Heat Index, look at the Heat Index Chart to the right. As an
example, if the air temperature is 95 degrees Fahrenheit (found on the
left side of the table) and the Relative Humidity is 55 percent (found
at the top of the table), the Heat Index — or how hot it really
feels — is 110 degrees Fahrenheit. This is at the intersection of
the 95 degrees Fahrenheit row and the 55 percent column. (Click
NOAA image for larger view of the NOAA Heat Index Chart. Click
here for high resolution version. Please credit “NOAA.”)
of the NOAA National Weather Service Heat Alert Procedures
NOAA National Weather Service will initiate alert
procedures when the Heat Index is expected to exceed 105 degrees Fahrenheit
- 110 degrees Fahrenheit (depending on local climate) for at least two
consecutive days. The procedures are:
Heat Index values in zone and city forecasts.
Special Weather Statements and/or Public Information Statements presenting
a detailed discussion of:
of the hazard, including Heat Index values
is most at risk
rules for reducing the risk.
state/local health officials in preparing Civil Emergency Messages in
severe heat waves. Meteorological information from Special Weather Statements
will be included as well, as more detailed medical information, advice
and names and telephone numbers of health officials.
to the media and over the NOAA
Weather Radio All Hazards all of the above information.
Heat Index used in issuing NOAA’s heat alerts should not be confused
with another related, yet different variable — NOAA’s Mean
Heat Index. The Mean Heat Index is a measure of how hot the temperatures
actually feel to a person over the entire course
of the day. It differs from the traditional Heat Index in that it is an
average of the Heat Index from the hottest and coldest times of each day.
waves often turn fatal when the nighttime temperature doesn't drop very
much from a high daytime temperature," said Jim Hoke, director of
the NOAA Hydrometeorological Prediction
Center in Camp Springs, Md., where the Mean Heat Index originates.
"The Mean Heat Index captures this potentially serious condition
by including data from what should be a cooler portion of the day, and
factoring that in to give a ‘big picture' of the day's temperatures,
not just the day's high."
to NOAA scientists, a Mean Heat Index above 85 degrees Fahrenheit is considered
dangerous. The Mean Heat Index is issued to the public via both graphical
and text formats, giving local health and emergency officials advanced
warning when a prolonged period of dangerous heat approaches. "Having
more time to warn the public increases the chances of saving lives,"
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 Fahrenheit. 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.
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 Fahrenheit) and high relative humidity,
the body is doing everything it can to maintain 98.6 degrees Fahrenheit
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.
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 (See call
out boxes below entitled "KNOW THESE HEAT DISORDER SYMPTOMS"
and "HEAT INDEX/HEAT DISORDERS").
severity, heat disorders share one common feature — the individual
has overexposed or over exercised for his/her age and physical condition
in the existing thermal environment. Ironically, 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.
Pose Special Hazards
The stagnant atmospheric conditions of the heat wave trap pollutants
in urban areas and add the stresses of severe pollution to the already
dangerously high temperatures, creating an even more serious risk for
inner-city death rates also may be attributed to the lack of/poor ventilation
and/or air conditioning — particularly in dwellings constructed
of materials such as brick that can trap hot, humid air at dangerous levels.
While air conditioning may be a luxury in normal times, it can be a lifesaver
during heat wave conditions.
NOAA Heat Health Watch/Warning System
NOAA Heat Health Watch/Warning System measures oppressive air masses affecting
health and is part of a national focus on the special hazards excessive
heat has on urban centers. As a result, this highly customized system
enhances NOAA’s ability to issue accurate and timely heat-related
advisories, watches and warnings and inform the public to take action
to avoid the health risks associated with periods of unusually high heat.
metropolitan areas in the United States are now a part of the NOAA National
Weather Service’s Heat Health Watch/Warning System. Cities Currently
with the Heat Health Watch/Warning System include: Portland, Ore.; Dallas/Fort
Worth, Texas; Phoenix, Ariz.; Yuma, Ariz.; Philadelphia, Pa.; Chicago,
Ill.; St. Louis, Mo.; Cincinnati/Dayton, Ohio; New Orleans, La.; Little
Rock, Ark.; Memphis, Tenn.; Shreveport/Monroe, La.; Lake Charles, La.;
Jackson/Meridian, Miss.; Seattle, Wash.; Washington, DC; Minneapolis/St.Paul,
is a health hazard in many urban areas and the Heat Health Watch/Warning
System provides heat information tailored specifically to your area,”
said retired Air Force Brig. Gen. David
L. Johnson, director of NOAA's National Weather Service. “People
in certain cities are accustomed to a more temperate climate. When it
gets unseasonably hot many people suffer, especially since many residences
do not have air conditioning.”
National Weather Service currently issues excessive heat products to provide
the nation advance notice of excessive heat events for the protection
of life and property," said Paul Stokols, NOAA National Weather Service
health services program leader. "These products are based on a single
heat index value derived from temperature and humidity. The Heat/Health
Watch/Warning System is a custom made system developed for each urban
area, based on specific meteorology for each locale, as well urban structure
was the first city in the United States to implement the Heat Health Watch/Warning
System program in 1997 and it has now become the worldwide model for heat
forecasting. In fact, studies
using three years of collected data indicate that 117
lives have been saved due to the Philadelphia heat program.
In the future, NOAA's National Weather Service plans to expand the number
of Heat Health Watch/Warning Systems from the current 17 cities to each
municipality with a population exceeding 500,000.
Although everyone is vulnerable to the dangers of extreme heat
— elderly persons, small children, chronic invalids, those on certain
medications or drugs (including 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.
a few things you can do to protect yourself from the dangers of heat waves:
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.
for summer. Lightweight light-colored clothing reflects heat
and sunlight, and helps your body maintain normal temperatures.
less fuel on your inner fires.
Foods (like proteins) that increase metabolic heat production also increase
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
not drink alcoholic beverages.
not take salt tablets unless specified by a physician.
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.
get too much sun. Sunburn makes the job of heat dissipation
that much more difficult.
Heat Disorders for People in Higher Risk Group:
Index of 130 degrees F or Higher:
Heatstroke/sunstroke highly likely with continued exposure.
Index of 105 degrees F - 130 degrees F:
Sunstroke, heat cramps or heat exhaustion likely, and heatstroke
possible with prolonged exposure and/or physical activity.
Index of 90 degrees F - 105 degrees F:
Sunstroke, heat cramps and heat exhaustion possible with prolonged
exposure and/or physical activity.
Index of 80 degrees F - 90 degrees F:
Fatigue possible with prolonged exposure and/or physical activity
THESE HEAT DISORDER SYMPTOMS
Redness and pain. In severe cases swelling of skin, blisters,
fever and headaches. First Aid: 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.
CRAMPS: Painful spasms usually in muscles of legs and
abdomen possible. Heavy sweating. First Aid: Firm pressure on
cramping muscles, or gentle massage to relieve spasm. Give sips
of water. If nausea occurs, discontinue use.
EXHAUSTION: Heavy sweating, weakness, skin cold, pale
and clammy. Pulse thready. Normal temperature possible. Fainting
and vomiting. First Aid: Get victim out of sun. Lay down and loosen
clothing. Apply cool, wet cloths. Fan or move victim to air conditioned
room. Sips of water. If nausea occurs, discontinue use. If vomiting
continues, seek immediate medical attention.
STROKE (or sunstroke):
High body temperature (106° F. or higher). Hot dry skin. Rapid
and strong pulse. Possible unconsciousness. First Aid: HEAT STROKE
IS A SEVERE MEDICAL EMERGENCY. SUMMON EMERGENCY MEDICAL ASSISTANCE
OR GET THE VICTIM TO A HOSPITAL IMMEDIATELY. DELAY CAN BE FATAL.
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. Persons on salt restrictive diets
should consult a physician before increasing their salt intake.
Produced as a cooperative effort
of NOAA’s National Weather Service, the Federal Emergency
Management Agency, and the American Red Cross. NOAA/PA 85001
NOAA National Weather Service
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1995–98 BY KRISTIE L. EBI, THOMAS J. TEISBERG, LAURENCE S. KALKSTEIN,
LAWRENCE ROBINSON, AND RODNEY F. WEIHER
Weather Service Public Affairs, (301) 713-0622