Is the secret to beating the heat as simple as throwing on a white shirt? A physicist breaks it down.

By Maggie Seaver
Updated: June 25, 2019

When it’s mid-August and almost too hot to function outdoors, I gravitate toward white clothing. Why? For starters, I find white tops and dresses do a stealthier job of hiding sweat (there, I said it). Second, most of my white clothes happen to be on the billowy side—because a skin-tight outfit is the last thing I need in such trying times. Finally, I stick to white because I’ve always blindly accepted the general knowledge that white clothing reflects the sun’s rays—or maybe it’s the heat. Or is it the light? 

Whatever scientific—or maybe pseudoscientific—hearsay has been circulating, I know I’m not the only one who's heard it. But is it true, or just a nice idea? And if it is a myth, is there something else we should all be wearing to prevent melting on the side of the road? 

To find out if white garments are truly the answer to warding off heat, I did the only reasonable thing I could think of: ask a physicist. Here, Rhett Allain, PhD, a professor of physics at Southeastern Louisiana University and the author of Wired magazine’s Dot Physics, helps explain where the 'white clothing helps keep you cooler" theory comes from—and why there are a few other factors to consider too.

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“For the most part, I would say white seems like it would be cooler,” Allain says. “Here’s a simple experiment to try: Take one white and one black piece of paper and lay them out in the sunlight. Wait maybe five minutes, then pick up the papers and hold them to your cheeks (cheeks are more sensitive to temperature than hands). I’d guess the black paper would feel hotter.” 

White light, Allain explains, is a combination of all the colors, while black light is no color. “That means the white paper reflects all the light and the black paper absorbs it and gets hotter.” 

Easy enough, right? But some research suggests dark or black clothing might be the answer to staying cool in the heat. For example, research published in 1980 analyzed why Bedouins choose to wear black garments to survive the Sinai desert heat.

In theory: “When your body gets hot, it radiates energy (in the infrared spectrum),” Allain says. “If you wear white clothes, this body radiation is reflected back to your body and heats you up even more, while black clothes would not reflect this body radiation.” 

But Allain doesn’t totally buy this theory (and the above study concluded otherwise, too: “the amount of heat gained by a Bedouin exposed to the hot desert is the same whether he wears a black or a white robe”). He wonders, since your body isn’t giving off normal light, but infrared light, would white clothing still reflect, and black clothing still absorb, infrared?

The answer to the question of whether or not to wear white for optimal temp control is both simple and complex: It depends. For example, what if you wear a very tight, thick white shirt? At that point, your body wouldn’t be giving off energy through radiation, but through thermal conduction (because your body’s touching the fabric). In this case, a looser, thinner dark shirt might be cooler than a thick or clingy white one.

“How a person feels in hot weather depends on many things: the color of their clothes, [whether their] clothes are tight or loose, how breathable the fabric [is], whether [there’s] a breeze, sun, or shade,” Allain says. You’re best bet? Wear what you’re most comfortable in. When in doubt, aim for soft, breathable fabrics (like cotton or linen) and give lighter shades a try.

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