Why Does Humidity Make Us Feel Hotter?

Tomwang112/iStock via Getty Images
Tomwang112/iStock via Getty Images

With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index—and why humidity makes us feel hotter.

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 that humidity refers to the amount of water contained in the air. 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 has 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 local meteorologist just needs to know the air temperature and the relative humidity, and the chart will tell him or her the rest.

Is the heat index 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 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, that's classified as "Extreme Danger" 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 "Danger" 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.

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This article has been updated for 2019.

Swear Off Toilet Paper With This Bidet Toilet Seat That's Easy to Install and Costs Less Than $100

Tushy
Tushy

The recent coronavirus-related toilet paper shortage has put the spotlight on the TP-less alternative that Americans have yet to truly embrace: the bidet.

It's not exactly a secret that toilet paper is wasteful—it's estimated to cost 437 billion gallons of water and 15 million trees to produce our yearly supply of the stuff. But while the numbers are plain to see, bidets still aren't common in the United States.

Well, if price was ever the biggest barrier standing in the way of swearing off toilet paper for good, there's now a cost-effective way to make the switch. Right now, you can get the space-saving Tushy bidet for less than $100. And you'll be able to install it yourself in just 10 minutes.

What is a Bidet?

Before we go any further, let’s just go ahead and get the awkward technical details out of the way. Instead of using toilet paper after going to the bathroom, bidets get you clean by using a stream of concentrated water that comes out of a faucet or nozzle. Traditional bidets look like weird toilets without tanks or lids, and while they’re pretty uncommon in the United States, you’ve definitely seen one if you’ve ever been to Europe or Asia.

That said, bidets aren’t just good for your butt. When you reduce toilet paper usage, you also reduce the amount of chemicals and emissions required to produce it, which is good for the environment. At the same time, you’re also saving money. So this is a huge win-win.

Unfortunately, traditional bidets are not an option for most Americans because they take up a lot of bathroom space and require extra plumbing. That’s where Tushy comes in.

The Tushy Classic Bidet Toilet Seat.

Unlike traditional bidets, the Tushy bidet doesn’t take up any extra space in your bathroom. It’s an attachment for your existing toilet that places an adjustable self-cleaning nozzle at the back of the bowl, just underneath the seat. But it doesn’t require any additional plumbing or electricity. All you have to do is remove the seat from your toilet, connect the Tushy to the clean water supply behind the toilet, and replace the seat on top of the Tushy attachment.

The Tushy has a control panel that lets you adjust the angle and pressure of the water stream for a perfect custom clean. The nozzle lowers when the Tushy is activated and retracts into its housing when not in use, keeping it clean and sanitary.

Like all bidets, the Tushy system takes a little getting used to. But once you get the hang of it, you’ll never want to use toilet paper again. In fact, Tushy is so sure you’ll love their product, they offer customers a 60-day risk-free guarantee. If you don’t love your Tushy, you can send it back for a full refund, minus shipping and handling.

Normally, the Tushy Classic retails for $109, but right now you can get the Tushy Classic for just $89. So if you’ve been thinking about going TP-free, now is definitely the time to do it.

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Why Did Noon Used to Mean 3 p.m.?

3 p.m. is basically noon for people who wake up at 12 p.m.
3 p.m. is basically noon for people who wake up at 12 p.m.
Mckyartstudio/iStock via Getty Images

If you’re a late sleeper, you might find yourself thinking 12 p.m. seems way too early to be considered midday, and the word noon would much better describe, say, 3 p.m. It turns out that ancient Romans would have agreed with you, if only for etymological reasons.

As Reader’s Digest explains, the days in ancient Rome were split into four periods of three hours each. The first hour was at sunrise around 6 a.m.—called prime, for first—followed by 9 a.m. (terce, denoting the third hour), 12 p.m. (sext, for sixth), and 3 p.m. (none, for ninth).

According to Merriam-Webster, Middle and Old English borrowed the time-keeping tradition, along with the Latin word for ninth, which was changed to nōn and eventually noon. Though we’re not sure exactly when or why noon started referring to 12 p.m. instead of 3 p.m., it could have something to do with Christian prayer traditions. In the Bible, Jesus’s crucifixion is said to have taken place at the ninth hour, and that’s when worshippers partook in their second of three daily prayers; the others were in the morning and evening. It’s possible that hungry monks were behind noon’s gradual shift from 3 p.m. to 12 p.m.—since their daily fast didn’t end until after the midday prayer, they had a built-in motive for moving it earlier.

While we didn’t exactly stay true to the original Latin meaning of noon, there’s another important remnant of ancient Rome hiding in the way we tell time today. Romans referred to 12 p.m. as meridiem, for midday, and so do we. A.M. is an abbreviation for ante meridiem, or before midday, and P.M. means post meridiem, or after midday.

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