The heat is on in the 612. In the 651, as well, all thanks to the 358.

358 is the area code for Finland, home of the Nordic practice of sauna. Now, a loose confederation of enthusiasts who make up the 612 Sauna Society is reigniting the ritual of the bench in Minnesota, and inviting the public to join them.

"It's a unique way of being with people," said John Pederson, who founded the 612 Sauna Society last year. "It's profoundly simple."

He knows that some may regard sauna as another hipster rediscovery alongside yoga and homebrewing. Maybe in some regions it is. "But in Minnesota, it's authentic."

Already, the 612 Sauna Society has almost 500 members, most from Minnesota, many of a millennial generation that is lighting a fire under this ancient tradition, here and across the country.

New York City long has had public saunas, especially the singeing hot Russian banyas. Oregon, natch, now has several, with Portland's Löyly getting the most buzz, its sauna water scented with "traditional smoky-smelling birch tar oil," its philosophy deemed "better living through radiance." Last year, San Francisco hosted the first Perfect Sweat Summit.

Yet Andrea Johnson, 33, of the portable Little Box Sauna hesitated at using the trend word, partly because sauna is so ancient.

"But more people who are doing it are talking to each other," she said. "We're doing sauna awareness."

On Nov. 27, they're firing up a portable sauna on Nicollet Mall, threatening to throw together in cozy quarters 10 to 12 strangers in swimsuits. "There's something different that happens when it's a collective activity," Johnson said.

Pederson, 33, discovered sauna while in Finland as a University of Wisconsin/Madison student. His host took him from the airport to a civic sauna, as if it was the most natural thing in the world.

Which it is. Many cultures have a sweat bathing practice, from American Indian sweat lodges to Turkish hammams.

"A good sweat may be the most honest thing humans still do," Pederson said. "But there's also this profoundness. I'm still unpacking why this resonates so much with me."

A place to unplug, recharge

Pederson likes to sauna with friends before heading out for an evening. "Everyone's bodies assimilate through the cycles of warming and cooling. We get synced up."

Such sociability may have special appeal to younger sauna sitters, whereas older people are drawn to wellness.

Glenn Auerbach, 53, of Minneapolis, has built a dozen saunas, written an eBook on building a sauna, and founded the Sauna Times (saunatimes.com), an online newsletter.

Auerbach said he loves sauna for its health benefits. "It's been monumental to me."

A recent 20-year study of Finnish men suggests that frequent saunas may help them live longer, with improved blood vessel function and lower blood pressure. The new study, in the Journal of the American Medical Association/Internal Medicine also linked longer sessions with fewer deaths from heart attacks, strokes and various heart-related conditions.

Such news plays well to Auerbach's baby boom demographic. Millennials have other, different, motivations.

"They are so plugged in all the time, it's hard for people of that age to drop that, so the sauna has become this wonderful place to do that, like a mini-vacation," he said.

"Then there's this real spirit of community, driven through social media. You see it in [Pederson's] work toward capturing like-minded people, and his generosity to bring people together. He wants people to leave reset and recharged."

Pederson, who grew up in St. Cloud, will be saunameister, or host, for the upcoming Little Box event. The sauna, with a striking charred-wood exterior, was built by two architect/designers at the University of Minnesota. Molly Reichert and Andrea Johnson each see sauna as a key to fostering community, especially this time of year.

"It's in winter when people lose their human connection to each other," said Reichert. They regard Little Box as a "mobile hot spot" to snag passing pedestrians and build a sense of place.

Last winter, they offered free saunas near Ikea, Radisson Blu and the Mall of America, "in Big Box land, which led to how the sauna got its name." The Nicollet Mall stint, next to Westminster Presbyterian Church, will offer free two-hour sessions, but reservations are required.

Sauna here has deep roots. The first Finnish immigrants arrived in 1864, their Nordic numbers joining Scandinavian immigrants who lived the sauna ethic. Summer camps expose some younger people to communal sauna, where they sweat out the grime of the wilderness. But back home, they're relegated to a fitness center's sauna.

One reason Pederson started the 612 Sauna Society was to connect, via Facebook, those who have saunas and those who seek the experience. The site also is a resource for building or buying a sauna.

Mostly, though, he's happiest when people simply post about their experience, or leave a note in his sauna guest book such as this one:

"This container is a portal to the eternal mirror/ And I guess we let the hiding stop here/ Let our electric body shed its tears./ Start over/ Start over/ Start over/ What is here, is good."

Don't sweat the shower

Little Box Sauna began as an experiment in "creative placemaking," through a grant from the National Endowment for the Arts and Artistry in Bloomington (formerly the Bloomington Theatre and Art Center). After the December sessions, Reichert and Johnson still want to get people in the sauna, so are making it available for rent to businesses or private parties. (Contact them via littleboxsauna.wordpress.com.)

To save time, here's everyone's first question: "Where's the shower?"

"The sauna is the shower," Reichert said. "We think of sweat as dirty, but a sauna sweat is incredibly cleansing." A dipper of cold water, a nearby garden hose or a plunge in a lake is nice for a sensory experience, but not for hygiene's sake.

Pederson will host the Nicollet Mall sauna, providing help, towels and good vibes to participants. Hosting, he said, is almost as satisfying as sitting on the bench.

"I thought I built my sauna to take care of myself, but then I realized I was doing this for other people, and they really enjoyed it and appreciated it," he said. "It's a simple act: Let me take care of you for a while."

Or, in the words of the 612's Sauna Society's motto: "Wasting time with dignity since 2014."

Kim Ode • 612-673-7185