I become seven years old the instant my body hits the water. I flap my arms and kick to a swim ladder, pulling myself out of the Willamette and onto the dock at Sellwood Riverfront Park. It’s New Year’s Day, and I’ve just biked across town with a bunch of strangers I’m now enthusiastically bossing about. “Again! Again!” I shout. We plunge again. Shivering, we scurry back to shore—and to the bracing heat of a sauna waiting in the parking lot.

Barrel-shaped and roomy, like a large cedar cigar, the sauna easily fits a dozen of us, and we take seats on facing benches. Chatter zips, laughter bounces. The door opens and we’re handed a ball of ice to place on the hot stones of the wood-burning stove, releasing fragrant steam.

This is Guss, a mobile sauna that allows Portlanders to hop between heat and a natural body of water. It’s a common contrast therapy tradition—Finns and Swedes break up sauna sessions with frigid dips in lakes and seas, and Russian banyas often sit next to water. Closer to home, a pair of mobile saunas in Bend spend winter by the Deschutes River, and Seattle has seen a proliferation of floating saunas. Portland, despite two major rivers and a respectable thermal bathing scene (Knot Springs, Cascada, Everett House, Löyly), hasn’t had such options. But in the past six months, it’s added two, plus a new sauna festival is taking over Milwaukie Bay Park this Valentine’s Day weekend.

Since the fall, Guss has posted up most weekends at Sellwood. It also appears once a month at North Portland’s Cathedral Park and once a month at Duality Brewing in Kerns (sans river). In November, owner Josh Gordon brought Guss to a “quantum listening event” at a waterfall in the Columbia River Gorge, and he’s got events ahead that pair sauna with fly-fishing and with snowshoeing. For Gordon, a cold plunge in a tub or tank “feels too sterile” compared to a river or lake. “It takes the fun out of it,” he says.

With its rooftop jumping platform, floating sauna Ebb & Ember is also questing for fun. “Cold plunging is hard,” says co-owner Jonah Moses. “When we were building this, it was, Hey, how can we bring some joy to this difficult task?”

Ebb & Ember, which opened in January, is moored on the Columbia, just south of Hayden Island. Moses and his partners bought the marina a year ago, and they dream of a sort of recreation-wellness playground here: paddleboard rentals, coffee shop, massage therapists. They’ve already got designs on additional saunas. For now, a lone, boxy sauna, heated by propane, bobs gently among houseboats. Big windows look out onto the water, and on my visit I watched a stream of boaters motor by. Gulls and cormorants flapped about. And the jump from the roof? Not bad.

This weekend’s Willamette Sauna Festivaali—that’s Finnish for “festival”—is the brainchild of Katie and Michael Calcagno, who opened the family-friendly SaunaGlo in downtown Milwaukie in late 2024. The fest will feature 20 saunas, mostly mobile (including one drawn by bicycle) and a handful of tent saunas, plus one constructed from polycarbonate panels—akin to a greenhouse—on a floating platform in the river.

Festival visitors can get swatted by bundles of birch by adding on a whisking session, or join a German sauna ritual called Aufguss, which involves steam and towel-twirling. A textiles showcase will feature alternatives to swimsuits—think dresses and shorts made from merino wool—and there will be live music, beer from Pfriem, and Finnish-style sausages. Plus, Michael Calcagno says, they’ll have lifeguards on duty for Willamette dips. “When you’re soaking next to a goose and a duck,” he says, “it’s a little different.”