Minnesota Is Battling Minus 28-Degree Weather. That’s Just How These Ultramarathoners Like It

As most Midwesterners hunker down inside amid historically bone-chilling temperatures, 146 extreme sports enthusiasts have been trekking across Northern Minnesota for one of the most excruciating endurance races in the world.

Arrowhead 135 — a 135-mile race that purposely takes place during the coldest stretch of winter in some of the most frigid locations in the continental United States — is wrapping up Wednesday afternoon with four remaining contestants making their way to the finish line.

Now in its 15th year, race directors Ken and Jackie Krueger say the average finish rate for the race is less than 50%, and the finish rate for new racers is even lower. Ken Krueger tells TIME that even if the four remaining contestants make it to the finish line, only 52 of the 146 participants would have completed the race — just 36%.

Racers begin at International Falls, Minnesota and can pick a mode of transport, which include bicycle, ski or foot. There are three checkpoints before they cross the finish line in Tower, Minnesota. The race, which began on Monday morning, is set to end by 7 p.m. on Wednesday, giving racers up to 60 hours to cross the finish line with little to no support.

This year’s forecast is one of the most daunting, with temperatures in Tower, Minnesota at minus-28 degrees on Wednesday and wind chills of 45 to 65 below zero, according to the National Weather Service.

But Krueger says participants are carefully vetted to ensure they can handle the punishing conditions.

“Folks are very well-prepared and make very smart decisions,” he says. “Racers have mandatory survival gear: at least a minus-20-degree-below rated sleeping bag, they’re required to have emergency calories, sleeping pads, insulated water containers, stove fuel and blinking lights and reflective vest, because the entire race takes place on a remote snowmobile trail.”

Profits from the race go to the Special Operations Warrior Foundation Charity, which provides college scholarships to children of killed and wounded U.S. Spec Ops; Together For Good, which provides short-term respite to children in need; and Falls Hunger Coalition, which provides food for families in need in Koochiching County, Minnesota.

Biker Don Gabrielson, 52, placed 15th in this year’s race, and tells TIME this is his fourth year competing. He says he finished the race three out of his four attempts, and that the daunting forecast is only part of the motivation to finish.

“This year it’s colder than normal, but there have been other years as cold and maybe even a little colder,” he tells TIME. “But that’s part of the challenge of this race — that it’s one of 50 hardest races in the world. Us racers come here specifically for that, and honestly for us it’s a sort of an exciting thing to say that we can make good decisions in those elements and overcome the challenges that we know we’re going to have … People here really study those things before they come to the race. The amount of preparation logistically, physically and mentally is very high — this is not a race you just wake up and decide to do.”

Gabrielson says part of the fun of the race is pushing himself.

“This is all about really understanding yourself in difficult situations and learning how to deal with things on a whole new level,” he says. “Every racer throughout here is a kindred spirit, in the perspective of really liking to understand how far human performance in extreme conditions can go.”