- The Washington Times - Friday, August 23, 2002

"Careful out there today, folks it's going to get up to 113 degrees." Well, not really. But when high humidity combines with temperatures in the 90s, Washington weathermen can't help but indulge in a bit of hyperbole.

More and more, meteorologists are reporting the heat index, or "apparent temperature," along with the actual mercury reading and sometimes in lieu of it. Whereas people once muttered curses about 90-degree days, they now get righteously indignant about triple-digit temperatures. The heat index offers not just a way to gauge the summer, but a chance to engage in a favorite pastime: complaining about the weather.

The National Weather Service's heat index is simple, in theory. The more humid it gets, the hotter the summer temperatures feel. The body stays cool by sweat evaporation, and it has to work extra hard when there's a layer of moist, warm air already blanketing the skin.

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So when the humidity stands at 50 percent not unusual for Washington and the mercury reaches 98 degrees, weathermen say it "feels" like 113 degrees.

OK, but 113 degrees where?

Someplace less humid than Washington, it turns out someplace like the desert Southwest. When it's 113 degrees in Phoenix, it's 113 degrees, period. The humidity is usually negligible.

"There's no comparison in D.C. or New York, as far as saturated air, compared to what happens in the Southwest," said Joe Moreno, meteorologist for KPNX-TV in Phoenix.

There, the humidity is often half of what Washington experiences, sometimes making the desert air even feel a few degrees cooler than the thermometer indicates.

So do Southwest weathermen ever feel tempted to say: "It's 113 degrees out, folks, but with the heat index it only feels like 98 so quit your bellyaching"?

"I sometimes will say that we're at 98 degrees, but that with the humidity it only feels like 90," Mr. Moreno said. "I'll also mention that it's 98 degrees in New York too, but with 60 percent humidity."

That's a whole different experience, as anyone who has walked around Manhattan in midsummer can testify; the heat index then would be at 123 degrees.

Which is not to say Arizona residents don't suffer in their own way.

"Some days, the moisture in the air is so low, you can feel your eyes dry up, your skin dry up," said Mr. Moreno.

In Bullhead City, northwest of Phoenix, it's not unheard of for the mercury to reach 120 degrees. But life is not so different there than it is on a muggy, 95-degree day in the District. "You get out and do your chores in the morning, before it gets hot," said Linda Rogers, who works in the air-conditioned office of Desert Lawn Funeral Home in Bullhead City.

She sympathized with District residents who struggle with the humidity. But she said there is an upside to the mugginess. "You see a difference in women who visit here from the East Coast they have nicer skin from being in that moist air all the time."

That moist air comes from the Gulf of Mexico, said Kevin Kulick, an Accuweather forecaster. Winds send warm, humid air from over the Gulf north and up along the East Coast.

It doesn't take a scientist to know summers in the District are hot and sticky. In the 1800s, British diplomats stationed in Washington received hardship pay for the sweltering heat. But it was only in 1979 that an Australian researcher named Robert Steadman found a way to quantify the suffering. His research assumes a comfortable humidity level for the human body about 35 percent and adjusts the "apparent temperature" upward as the humidity rises.

Today his research has been incorporated into regular National Weather Service bulletins and heat warnings.

"Heat is an underrated killer," said Mark Tew, senior meteorologist with the National Weather Service. He puts the average number of heat deaths at more than 200 per year and said more Americans die this way than from floods, lightning, tornadoes and hurricanes combined.

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