This California basin has one of the hottest fumaroles on Earth, and it’s named after the guy who lost his leg finding it
There’s a fumarole in Northern California hot enough to rank among the hottest in the world, and it’s sitting inside a national park most people drive straight past on their way to Tahoe or Shasta. Big Boiler, deep in a basin called Bumpass Hell, has been measured at 322 degrees Fahrenheit. That’s not a typo — steam that hot could put a serious hurt on you in seconds.
Ever wonder how a place earns a name like that? Ask Kendall Bumpass.
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In 1865, Bumpass was leading a newspaper editor out to see the area when he broke through a thin crust covering a mudpot and burned his leg badly enough that it had to be amputated. The basin took its name from how he described the place afterward, and it never let go.
What’s left of that basin today is the largest hydrothermal area inside Lassen Volcanic National Park — about 16 acres of roaring fumaroles, thumping mud pots, and milky boiling pools, all connected by a boardwalk. It’s about as close as California gets to Yellowstone, minus the geysers and most of the crowds.
Getting there means an easy-to-moderate hike: 3 miles round trip, roughly 90 minutes to two hours, mostly flat for the first mile before it drops 300 feet into the basin over the final stretch. The trailhead sits around 8,200 feet, so give yourself a minute to adjust if you’re coming from sea level.
Here’s the timing catch: the trail is closed most of the year and only opens once the snowpack clears, typically sometime between late June and October depending on the winter. This year it opened June 26 — one of the earliest openings in over a decade — so it’s been open and accessible all summer.
Stay on the boardwalk the whole way through. The National Park Service has documented visitors airlifted out after stepping off marked trails in the park’s hydrothermal areas — the ground can look solid and still be a thin crust hiding acidic water hot enough to burn straight through skin.
You’ll need an entrance pass to get into the park — $30 per vehicle from mid-April through November, less in winter. If you’re planning to hit more than one national park this year, an America the Beautiful Pass covers Lassen’s entrance fee too.
Parking at the trailhead is limited and tends to fill by mid-morning on weekends, so an early start pays off twice over — smaller crowds and an actual spot to park in. There are vault toilets at the trailhead but none out on the trail, and pets aren’t allowed here at all.
Trail’s full or the timing doesn’t line up? Sulphur Works, a mile north of the park’s southwest entrance, gets you boiling mud pots and steam vents right off a roadside sidewalk, no hike required. My pick is still Bumpass Hell, though — nothing else in the park puts you this close to something this alive.
Have you made it out to Lassen, or is it still one of those California parks that stays permanently on the someday list? It’s a strange, quietly wild corner of the state, and it deserves more than a drive-by.
Trip tips: grab a rental car to get out here, lock in your hotel before the good rooms are gone, or skip both and book a camper van instead.
Rules and fees change — always confirm current requirements before you go.
