Swimming Outdoors in Winter? Some Love It. but Bring a Swim Parka.

Special to The Washington Post / Marlene Cimons

13:18 JST, December 11, 2023

It’s 6:45 a.m. and cold – in the mid-30s – when I step onto the Bethesda-Chevy Chase YMCA’s outdoor pool deck, a towel wrapped around my shoulders. Pink streaks punctuate the sky, and I can still see the moon. A canopy of steamy vapor hovers above the heated water. I sink into the pool and start swimming, the contrast of bracing air and warmish water exhilarating.

Think I’m crazy? You’re not alone. It’s difficult for some to imagine swimming outside when it’s near freezing. But outdoor winter swimming in a heated pool is safe, experts say, and good for your health. For the dedicated cadre of outdoor winter swimmers who join me every morning, there’s nothing like it.

“It’s a pleasure to feel so alive,” says Valerie Campbell a Kensington, Md., massage therapist who swims outside at the Y five mornings a week all year long. “We enjoy the sunlight, the fog over the water, even the brutal wind at times, which can chill the heels of our feet as we kick. Sometimes people from ‘inside’ come out, but they never last long,” referring to indoor swimmers.

An outdoor swim on a cold evening also can be awe-inducing. Robert Judson, a financial consultant from Bethesda, Md., recalls the one time he missed his usual sunrise swim and made it up after work. “It was a pitch-dark cold night with the stars out,” he says. “It began snowing very lightly midway through my usual slow mile. It was perfect. Perhaps too perfect. Maybe it was a dream.”

Non-swimmers and even those who swim inside don’t always understand the passion for winter swimming. But they are okay with it, even grateful. “I am delighted that there are so many nuts who love swimming outdoors,” says Kate Macomber Stern, a teacher who swims 45 minutes daily in one of the B-CC Y’s two indoor pools. “That makes the indoor pools much less crowded.” (Such appreciation works both ways.)

Although it can feel particularly invigorating, experts say that health-wise, swimming in a heated pool outdoors doesn’t provide any more health benefits than indoor swimming.

Cold air doesn’t affect the calories you burn, although swimming in cold water can – if shivering is added to swimming, says Mike Tipton, professor of human and applied physiology at the University of Portsmouth’s School of Sport, Health and Exercise Science. “This is a miserable experience. The shivering disappears when you exercise at an intensity above ‘light exercise.'”

In warm waters outdoors (the B-CC Y usually keeps the water between 80 and 83 degrees), there is little danger of hypothermia – or abnormally low body temperature that can occur from exposure to extreme cold – once a swimmer starts moving, experts say. Unlike in unheated outdoor waters, a swimmer’s body fat isn’t that important, they say.

“Once you are in the [heated] water, the thermoregulatory aspect” – the body’s ability to maintain a safe temperature – “is normal,” says Scott Trappe, director of the human performance laboratory and professor of human bioenergetics at Ball State University. “There is nothing in that scenario that would cause a thermoregulatory risk.”

People need to distinguish between water and air temperatures, because “once you get into the pool, the cool air isn’t a factor,” Trappe says. “You stay submerged. It’s perfectly fine. In fact, it’s wonderful.”

I’m a slow swimmer, so for me, an 82-degree pool is ideal. But faster swimmers like Anna Alberini, an economics professor at the University of Maryland, prefer water cooler than 80 degrees, although not below 70. When it’s too warm, she says, “I feel like I’m swimming in soup and wouldn’t be shocked if I swam into a potato.”

The risk of hypothermia increases when the water temperature drops into the 70s or lower. This is one reason many competitive open-water lake and river swimmers train in outdoor heated pools during the winter.

“If we’re talking only winter, I typically don’t swim in open water then,” says Diane McManus a teacher from Upper Darby, Pa., who swims in the Schuylkill River through October. “I like the pool because it’s easier to get in and out and still has some closeness to nature – looking up at the stars during night swims, enjoying the sunrise in the dawn swims.”

In February 2022, she made an exception to compete in the Lake Memphremagog Winter Swimming Festival in Newport, Vt., where two lanes are cut into the frozen lake and the event is conducted like a regular swim meet – with spectators dressed in snow parkas, hats and boots. McManus is an experienced river and lake swimmer, acclimatized to swimming in ridiculously cold conditions. This contest had both: 30-degree water and 1 degree air, she recalls.

“They had to keep monitoring the water so it wouldn’t refreeze,” she says. “I did just 25-meter events,” which are mercifully short. “It was challenging but pretty amazing, too,” she says.

When the water is very cold, below 70 degrees, swimmers must take precautions and adapt, experts say. This means exposing themselves to cold water gradually over time, says Michael J. Joyner, physiologist and anesthesiologist at the Mayo Clinic in Rochester, Minn. “If the water temperature is really uncomfortable and you’re not used to it, you need to be careful,” he says. “If the temperature is below 70, get in for a few minutes today, then a few minutes tomorrow and so on.”

How long does it take? “It’s variable,” Joyner says. “But temps that once felt cold can feel not so cold in a matter of days or a week.

Both the B-CC and Silver Spring, Md., YMCA facilities offer year-round outdoor swimming. Lifeguards, who often wear sweatpants and hoodies or swim parkas (long fleece-lined coats with a waterproof exterior) over their swimsuits, rotate every half-hour and have a small, heated shack available to protect them from cold, wind and rain. (Yes, outdoor swimmers also love swimming in the rain.) When the air is below freezing or the wind chill dips below 25, the pool closes until both rise. This protects against people slipping if water splashes on the deck and freezes.

Should you wear a wet suit? Nah. It’s only good for very cold water, experts say, when the water temperature dips below 76 degrees. In fact, you may feel too hot if you wear one in a heated pool.

Also, experts say, don’t soak in the hot tub before going outside to swim. “If you get in that hot water, you are setting yourself up for having the outdoor pool feel much colder,” Trappe says. So save the hot tub for after the swim.

As for getting into the outdoor pool, a big towel, bathrobe or swim parka is usually enough to make it from the locker room to the water and back again. Some swimmers don’t bother, though. “It only takes a minute or two to get into the water, and I can survive that long,” Campbell says. “It takes longer to put on a covering or take it off, and I’m already warm from my swim when I get out.”

I swim for 45 to 60 minutes and, after I get out, don’t linger outdoors to talk. Instead, I head straight to the indoor hot tub. “In the summer, you can have those conversations on the deck,” Trappe says. “In the winter, you can have the same conversations – but in the locker room.”