If we find ourselves outdoors, we are walking without an umbrella and suddenly it starts to rain, what should we do? Running or walking? It seems like a trivial question, but for decades it has been at the center of scientific studies, debates between physicists and even television tests. Running very strong we reduce the time spent in the rain, but we risk getting more wet on the front and maybe even ending up in a puddle. Walkinghowever, we stay in the rain longer, but the water will come on us with lower intensity.
Numerous studies have addressed the problem, also trying to establish what is the best speed at which to move. The only case in which the answer is shared by almost everyone is with the wind at your back: if we run around to the same wind speedthe drops behind us “don’t reach us” and we get less wet. In other cases, the general rule is: running makes you less wetbecause we pass less time in the rain. But you don’t need to be a hundred-metre runner: run faster than 12km/h it doesn’t change much how wet we will get and we will only arrive more tired. Let’s see why this problem is not easy to study, what the theory tells us and what they observed when they tested the theory for real.
Why this problem is so difficult to study
At first glance, decide whether run or walk in the rain It seems simple, but answering precisely is far from easy: they are there many variables at stake and this is precisely why physicists and meteorologists have been challenging each other with increasingly precise simulations for decades.
First of all, we must consider that rain and wind are not constant: during a downpour, the intensity and the direction they can change several times. Then there is the risk of get wet from belowending up in puddles or splashing if you run too fast. And the faster you go, the higher the risk of slip and soak your pants.
Another variable is the body shape: A tall, stocky person gets hit by more drops than a short, petite one, but can take longer steps and get to cover sooner.
All these factors make the problem extremely complex to simulate. Precisely for this reason, since the 1970s the scientific community has been trying to identify an “ideal speed” to get wet as little as possible, but There is no definitive answer, valid in every situation, yet. Let’s look at the most famous studies.
Why you get less wet while running: studies
In 1995, the University of Reading studied a very simplified case, with no wind and uniform rain, and found that making a sprint at 20 km/h instead of speeding along at 10.8 km/h reduced the quantity ofwater absorbed only by 10%. The authors concluded that a sprint can be useful if the rain is about to intensify, but that in general it is better to run at a moderate speed, hoping that it will stop soon.
In 1997 these results were improved by Peterson and Wallis, two researchers from the National Climatic Data Center, who introduced more realistic variables such as wind direction and rain intensity. By their calculations, running offered greater benefits: with light rain and no wind, reduced the absorbed water of 16%while with pouring rain and head-on wind the reduction reached up to 44%.
In 2012, Franco Bocci, of the University of Brescia, developed an even more precise model, considering body shape, runner’s inclination and wind speed. His results showed that, in general, There is no optimal speed that is valid for everyonebut, in the absence of wind or with rain against the wind, it’s better to run as quickly as possible, while with the wind at your back the ideal speed depends on your body type and the intensity of the rain.
Finally, in 2023, a research group from the École des Ponts ParisTech used real rain and wind datasimulating variable conditions for twenty consecutive minutes. Here too the conclusion was similar: run at approx 12km/h reduces the amount of water received in most cases, with a decrease of more than 50% in more than half of the cases considered. However, accelerating to the maximum and going at 18 km/h is not necessarily useful: in many scenarios you get almost equally wet (indeed, sometimes even more), but you struggle much more.
It’s actually been tested: running is better
The problem has not remained confined to theoretical simulations. Was actually tested both by Peterson and Wallis in the study of 1997both by the conductors of MythBusters – Myths to dispel, a scientific popularization program broadcast by Discovery Channel.
In their experiment, Peterson and Wallis traced a path to 100 meter ring and, to precisely measure how much water was absorbed, they wore identical clothes with two large plastic bags under their clothes. They waited for a day of heavy rain (15-20 mm/h), weighed their dry clothes and then walked the route at different speeds: 14.4 km/h for the runner and 5 km/h for the walker. Finally, they weighed the wet clothes again: the walker had collected 217 grams of water, the runner only 130 grams. A reduction of approximately 40%perfectly in line with their simulations.
A similar test was conducted years later by the MythBusters, who wore identical suits in very heavy artificial rain to compare how wet they got while walking or running. The first test they did seemed to show the exact opposite: those who ran were wetter! This result, however, was highly contested, especially because the artificial rain it did not represent realistic conditions. For this reason, in a subsequent episode of MythBusters Revisited, the authors decided to repeat the test in real rain. This time the result confirmed the theory: running really makes you less wet.
