CLOSE
Original image
Getty Images

What Exactly Is the Heat Index?

Original image
Getty Images

Is it really not the heat, but the humidity? With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index.

Why does humidity make us feel hotter?

To answer that question, we need to talk about getting sweaty.

As you probably remember from your high school biology class, one of the ways our bodies cool themselves is by sweating. The sweat then evaporates from our skin, and it carries heat away from the body as it leaves.

Humidity throws a wrench in that system of evaporative cooling, though. As relative humidity increases, the evaporation of sweat from our skin slows down. Instead, the sweat just drips off of us, which leaves us with all of the stinkiness and none of the cooling effect. Thus, when the humidity spikes, our bodies effectively lose a key tool that could normally be used to cool us down.

What’s relative about relative humidity?

We all know humidity is the amount of water the air contains. However, as the air’s temperature changes, so does the amount of water the air can hold. (Air can hold more water vapor as the temperature heats up.) Relative humidity compares the actual humidity to the maximum amount of water vapor the air can hold at any given temperature.

Whose idea was the heat index?

While the notion of humidity making days feel warmer is painfully apparent to anyone who’s ever been outside on a soupy day, our current system owes a big debt to Robert G. Steadman, an academic textile researcher. In a 1979 research paper called, “An Assessment of Sultriness, Parts I and II,” Steadman laid out the basic factors that would affect how hot a person felt under a given set of conditions, and meteorologists soon used his work to derive a simplified formula for calculating heat index.

The formula is long and cumbersome, but luckily it can be transformed into easy-to-read charts. Today your weatherman just needs to know the air temperature and the relative humidity, and the chart will tell him the rest.

Is the calculation the same for everyone?

Not quite, but it’s close. Steadman’s original research was founded on the idea of a “typical” person who was outdoors under a very precise set of conditions. Specifically, Steadman’s everyman was 5’7” tall, weighed 147 pounds, wore long pants and a short-sleeved shirt, and was walking at just over three miles per hour into a slight breeze in the shade. Any deviations from these conditions will affect how the heat/humidity combo feels to a certain person.

What difference does being in the shade make?

Quite a big one. All of the National Weather Service’s charts for calculating the heat index make the reasonable assumption that folks will look for shade when it’s oppressively hot and muggy out. Direct sunlight can add up to 15 degrees to the calculated heat index.

How does the wind affect how dangerous the heat is?

Normally, when we think of wind on a hot day, we think of a nice, cooling breeze. That’s the normal state of affairs, but when the weather is really, really hot – think high-90s hot – a dry wind actually heats us up. When it’s that hot out, wind actually draws sweat away from our bodies before it can evaporate to help cool us down. Thanks to this effect, what might have been a cool breeze acts more like a convection oven.

When should I start worrying about high heat index readings?

The National Weather Service has a handy four-tiered system to tell you how dire the heat situation is. At the most severe level when the heat index is over 130, the day is classified as “extremely hot,” and the risk of heat stroke is “highly likely” with continued exposure. Things get less scary as you move down the ladder, but even on “very hot” days when the heat index ranges from 105 to 130, you probably don’t want to be outside. According to the service, that’s when prolonged exposure and/or physical activity make sunstroke, heat cramps, and heat exhaustion likely, while heat stroke is possible.

What’s the highest heat index that’s been recorded?

In their book Extreme Weather Christopher C. Burt and Mark Stroud tackle this topic. The authors explain that the worst spots in the world for a combination of heat and humidity are along Ethiopia’s Red Sea coast, along Somalia’s Gulf of Aden coast, and around the Persian Gulf. July 8, 2003, was a particularly punishing day in Dharan, Saudi Arabia. That day the temperature hit 108 Fahrenheit with a dew point of 95 degrees. This combination led to a heat index in the neighborhood of 155 to 160.

This article originally appeared in 2011.

Original image
iStock
arrow
Big Questions
Why Do Cats Love Scratching Furniture?
Original image
iStock

Allergy suffering aside, cat ownership has proven health benefits. A feline friend can aid in the grieving process, reduce anxiety, and offer companionship.

The con in the cat column? They have no reservations about turning your furniture into shredded pleather. No matter how expensive your living room set, these furry troublemakers will treat it with the respect accorded to a college futon. Do cats do this out of some kind of spite? Are they conspiring with Raymour & Flanigan to get you to keep updating home decor?

Neither. According to cat behaviorists, cats gravitate toward scratching furniture mostly because that love seat is in a really conspicuous area [PDF]. As a result, cats want to send a message to any other animal that may happen by: namely, that this plush seating belongs to the cat who marked it. Scratching provides both visual evidence (claw marks) as well as a scent marker. Cat paws have scent glands that can leave smells that are detectable to other cats and animals.

But it’s not just territorial: Cats also scratch to remove sloughed-off nail tips, allowing fresh nail growth to occur. And they can work out their knotted back muscles—cramped from sleeping 16 hours a day, no doubt—by kneading the soft foam of a sectional.

If you want to dissuade your cat from such behavior, purchasing a scratching post is a good start. Make sure it’s non-carpeted—their nails can get caught on the fibers—and tall enough to allow for a good stretch. Most importantly, put it near furniture so cats can mark their hangout in high-traffic areas. A good post might be a little more expensive, but will likely result in fewer trips to Ethan Allen.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

Original image
iStock
arrow
Big Questions
Who Was Chuck Taylor?
Original image
iStock

From Betty Crocker to Tommy Bahama, plenty of popular labels are "named" after fake people. But one product with a bona fide backstory to its moniker is Converse's Chuck Taylor All-Star sneakers. The durable gym shoes are beloved by everyone from jocks to hipsters. But who's the man behind the cursive signature on the trademark circular ankle patch?

As journalist Abraham Aamidor recounted in his 2006 book Chuck Taylor, All Star: The True Story of the Man behind the Most Famous Athletic Shoe in History, Chuck Taylor was a former pro basketball player-turned-Converse salesman whose personal brand and tireless salesmanship were instrumental to the shoes' success.

Charles Hollis Taylor was born on July 24, 1901, and raised in southern Indiana. Basketball—the brand-new sport invented by James Naismith in 1891—was beginning to take the Hoosier State by storm. Taylor joined his high school team, the Columbus High School Bull Dogs, and was named captain.

After graduation, instead of heading off to college, Taylor launched his semi-pro career playing basketball with the Columbus Commercials. He’d go on to play for a handful of other teams across the Midwest, including the the Akron Firestone Non-Skids in Ohio, before finally moving to Chicago in 1922 to work as a sales representative for the Converse Rubber Shoe Co. (The company's name was eventually shortened to Converse, Inc.)

Founded in Malden, Massachusetts, in 1908 as a rubber shoe manufacturer, Converse first began producing canvas shoes in 1915, since there wasn't a year-round market for galoshes. They introduced their All-Star canvas sports shoes two years later, in 1917. It’s unclear whether Chuck was initially recruited to also play ball for Converse (by 1926, the brand was sponsoring a traveling team) or if he was simply employed to work in sales. However, we do know that he quickly proved himself to be indispensable to the company.

Taylor listened carefully to customer feedback, and passed on suggestions for shoe improvements—including more padding under the ball of the foot, a different rubber compound in the sole to avoid scuffs, and a patch to protect the ankle—to his regional office. He also relied on his basketball skills to impress prospective clients, hosting free Chuck Taylor basketball clinics around the country to teach high school and college players his signature moves on the court.

In addition to his myriad other job duties, Taylor played for and managed the All-Stars, a traveling team sponsored by Converse to promote their new All Star shoes, and launched and helped publish the Converse Basketball Yearbook, which covered the game of basketball on an annual basis.

After leaving the All-Stars, Taylor continued to publicize his shoe—and own personal brand—by hobnobbing with customers at small-town sporting goods stores and making “special appearances” at local basketball games. There, he’d be included in the starting lineup of a local team during a pivotal game.

Taylor’s star grew so bright that in 1932, Converse added his signature to the ankle patch of the All Star shoes. From that point on, they were known as Chuck Taylor All-Stars. Still, Taylor—who reportedly took shameless advantage of his expense account and earned a good salary—is believed to have never received royalties for the use of his name.

In 1969, Taylor was inducted into the Basketball Hall of Fame. The same year, he died from a heart attack on June 23, at the age of 67. Around this time, athletic shoes manufactured by companies like Adidas and Nike began replacing Converse on the court, and soon both Taylor and his namesake kicks were beloved by a different sort of customer.

Still, even though Taylor's star has faded over the decades, fans of his shoe continue to carry on his legacy: Today, Converse sells more than 270,000 pairs of Chuck Taylors a day, 365 days a year, to retro-loving customers who can't get enough of the athlete's looping cursive signature.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios