When you’re outdoors and it starts to rain, does running (rather than walking) to the nearest shelter really keep you any drier? asks a reader.
It begins to pour. You have no umbrella, or printed newspaper. (The internet, alas, won’t keep your head dry.) Never mind singing in the rain. The question is, To run or not to run?
Assuming you’re healthy enough for a mad dash to that building across the street (or the shelter house in a public park), is it worth the energy? Can you really slip between the drops? Or will sprinting through a downpour actually make you wetter?
At first glance, the answer appears obvious: Running means less time spent in the rain, and less-wet clothing. But the walking advocates have arguments that seem to make sense, too. If you run through falling raindrops, they point out, you’ll catch more raindrops on the front of your body — chest, stomach, fronts of legs. If you walk, most of the drops will fall on your head. Since the front of your body has more surface area than the top of your head and shoulders, you’ll get more water-logged if you run into the wall of rain.
Some have even done mathematical simulations that say you’ll be wetter if you run. With rain falling straight down from the sky, and no wind, they argue, you’ll scoop up water through the rain field as you dash forward. But actual experiments with real human beings have found otherwise.
According to physicist Jearl Walker, of Cleveland State University, running keeps you drier because you spend less time being pelted with water. If there’s no wind, or the wind is blowing toward you, Walker says, you can minimize the number of drops your body encounters by leaning forward, while running as fast as you can. With a wind at your back, he advises matching your speed to that of the horizontally blowing drops. Moving with the rain, he says, you’ll avoid both front and back splatters; most drops will strike your head.
And in a 1997 report in the British journal Weather, two climate researchers in Asheville, NC also found that running trumps walking. On a rainy day, Trevor Wallis and Thomas Peterson suited up in identical sweats, wearing trash bags underneath so that water wouldn’t soak through. One ran and the other walked through the pouring rain over a 100-meter (328-ft.) course, weighing their track suits before and after their wet dash/stroll. What they found: The clothes of Wallis, who ran, were a full 40 percent drier.
If you’re already soaked, or the nearest shelter is very far away, it probably doesn’t matter whether you walk or jog. To find out if it’s really worth breaking into a run in the rain, physicist Doug Craigen has devised a handy calculator. You’ll need to enter your height, take some body measurements, and guess at the wind speed of your own rainy day. Find out how wet you’ll get at http://www.dctech.com/physics/features/0600.php.