|Recent deaths show how high
temperatures pose danger
Special to the Mercury News
In recent weeks, there have been several tragic stories about
heat-related deaths of children in cars, the elderly and even
well-conditioned athletes. These events demonstrate that heat is the
most deadly weather phenomenon in the United States, causing an average
of 144 deaths per year. According to statistics from the National
Weather Service, each year heat kills more people than floods,
lightning, tornadoes, cold weather or hurricanes.
These numbers only account for fatalities directly related to heat.
There are undoubtedly many more deaths indirectly related to hot
weather, especially among the elderly during heat waves.
For example, in 1980 a severe heat wave in the Midwest killed more
than 1,250 people. Officials from the federal Centers for Disease
Control and Prevention estimated another 10,000 deaths were related to
heat stress. Here in the Bay Area, there were nine heat-related deaths
in June 2000 when temperature readings ranged from 100 degrees to 110
Additionally, there is a great deal of truth in the expression:
``It's not the heat, it's the humidity.'' Not only is high humidity
uncomfortable, it is also unhealthy. Heat-related illness occurs when a
person's body can't properly cool itself by perspiring. Under extremely
hot or humid conditions, sweating can't compensate enough to stave off a
rapid rise in body temperature. The body's inability to cool itself is
exacerbated when the humidity is high.
Ultimately, very high body temperatures may damage the brain or other
The recent death of Minnesota Vikings player Korey Stringer was a
prime example of this phenomenon. Stringer suffered heatstroke at
training camp July 31, when the temperature was in the low 90s. But the
relative humidity that day was about 50 percent and the ``heat index,''
which combines the two factors, was more than 100 degrees.
The heat index is a measure of the apparent temperature and relates
to the body's ability to cool itself. It is calculated from the ambient
temperature and the relative humidity. A table showing this relationship
can be found online at
http://ggweather.com/101/hi.htm, and there is an online
A number of factors affect the body's ability to cool itself during
extremely hot weather. Besides humidity, other conditions that can
increase risks from heat include age, obesity, fever, dehydration, heart
disease, mental illness, poor circulation, sunburn, prescription drug
use and alcohol use. Infants and children up to four years of age and
people older than 65 are also at high risk.
In the Bay Area, high humidity is often less of a concern that it is
in other parts of the country. But we have other concerns to keep in
mind -- our frequent sunshine and our car culture.
Extreme heat can arise easily in enclosed vehicles. A number of
studies have shown that the temperature in an enclosed car or truck can
be more than 30 degrees above the outside temperature after less than 20
minutes, and more than 40 degrees within a half-hour.
On a recent 80-degree day in San Jose, after an hour in the sun, my
car was a toasty 136 degrees. This reading was taken with the
thermometer out of direct sunlight. If the thermometer is in direct sun,
the results are even more dramatic -- I recently recorded a rise from 80
to 103 degrees in only 5 minutes!
Keep this in mind when considering leaving a child or pet in a car
for even a minute or two. Already this year, at least 27 children have
died in cars due to excessive heat. State Sen. Jackie Speier, D-San
Mateo, has sponsored a bill (SB 255) that is working its way through the
Legislature. It would place penalties on people who leave a child who is
6 years old or younger unattended in a vehicle.
Q I've heard people talk about
90-degree temperatures and 90 percent relative humidity. What would the
heat index be under these conditions? Tom Robinson - Redwood City
A Actually, these 90-90
conditions are a myth and do not occur naturally. For this to happen the
dew point, the temperature that moist air must be cooled to for
condensation to occur, would have to be at least 87 degrees -- and the
highest that I have ever seen is about 82 degrees. With a temperature of
90 degrees and a dew point of 82, the relative humidity would be only 77
percent. This would translate to a heat index of 111. If it were
possible to get to 90 degrees and 90 percent relative humidity, the heat
index would be 122 degrees.
Q I am interested in heat
index conditions across the country. Are there any sites that show the
heat index in other parts of the country? The Web sites we have found
provide good information about what the heat index is, but they don't
give current readings. Gordon Kass - Los Gatos
A There is a very good Web site
that shows not only a current map of the heat index of the nation, but
it also has forecast heat index values for the next 24 hours. See