Membership to one of the most exclusive clubs in the world takes place around a short red and white striped pole in Antarctica. Only those who endure an atmospheric difference of 300 degrees Fahrenheit are granted entry.

To join the elite 300 Club, residents at the Amundsen-Scott South Pole Station, where on winter days the outside temperature dips below -100 degrees, must bare it all. It’s an odd tradition, one that comes with a high risk of frostbite in rather sensitive, traditionally clothed areas.

To join the exclusive group, the scientists must first spend time in the station’s 200-degree sauna. Once they’re fully cooked, they dash outside (at a brisk walk, because running is dangerous) wearing nothing but shoes and an optional neck gaiter to circle the ceremonial South Pole marker, which is hundreds of feet from the station. They then get back into the steamy sauna, which helps thaw their outsides while a bit of alcohol warms them up inside. Those who complete the challenge even earn a commemorative patch.

Though the thought of a naked scientist racing across the ice in dangerously cold temperatures to circle a pole may seem simply absurd, it’s actually a beloved ritual. The temperature only gets low enough a handful of days each year, giving the wacky tradition an almost ceremonial feel. Participants are usually cheered on by bystanders who use flashlights to guide them to the pole during the perpetual winter blackness.

The marker isn’t even the true location of the South Pole. Antarctica is blanketed by massive chunks of moving ice sheets that move about 30 feet each year. The ice’s inability to sit still makes pinpointing the world’s most southern spot with permanent precision impossible.

Finding and marking the accurate geographic South Pole is an annual (fully clothed) New Year’s Day tradition for those staying at the station. Every year since 1959, South Pole residents erect a new temporary marker at the spot and retire the old one into a display case inside the station. The ceremonial South Pole remains where it is, flanked by the flags, awaiting the next group of winter scientists hoping to join one of the world’s weirdest clubs.