Yellowstone is home to a greater number of thermal features (about 10,000) than anywhere else in the world. It just so happens to also be home to the greatest density of signage and warnings telling you to stay away from them. Consequently, there are only a few spots in the park where it’s legal to soak, and the best of these is the Boiling River, about five miles on the Gardner side of Mammoth.
What Makes It Great
Part of one sign says, ‘‘Many of Yellowstone National Park's waters have been shown to contain organisms that are known to cause skin rashes, infections and/or primary amoebic meningitis—which can be quickly fatal—and Legionnaires Disease.'' The sign goes on to advise bathers 1) not to submerge their heads and 2) to avoid inhalation of thermal steam.
I’ve only soaked in the Boiling River once. It was over a year ago and I have not yet come down with primary amoebic meningitis or Legionnaires Disease. On busy summer days, up to 200 people soak in the Boiling River. No one has yet come forward saying they’ve gotten sick there. I hope the streak continues through your visit.
A mellow 1/2-mile walk along the Gardner River takes you to the Boiling River. The latter, as a six-foot wide stream, plunges over travertine rocks into a 150-foot-long band of soaking pools along the side of the former.
Who is Going to Love It
If you want to wait until the temperatures get even more hot-spring-y—i.e., winter—you can. As with most natural hot springs, temperatures in the pools vary and are often interrupted by currents flowing in from the Gardner. There is more than one sweet spot though.
Directions, Parking, & Regulations
At the parking lot for the river, there's a vault toilet where you can change into and out of bathing suits. There are also signs warning of the potential dangers of soaking in the Boiling River.
The Boiling River and the Gardner entrance to the park are open year-round. But after the park roads start to close October 15 (the south entrance is open until November 5), you have to take a snow coach from Flagg Ranch to Mammoth or drive all the way around.
The Boiling River is open from dawn until dusk. Aside from the fee required to enter Yellowstone, it is free.