On the first day of summer every year, a group of hikers traipses through the woods in the buff to be one with nature.
They've dubbed the tradition Naked Hiking Day.
This time around, the summer solstice is on Father's Day — and those who prefer to go outside with clothes on are fuming.
Park rangers and police have threatened that anyone caught outside naked could be charged with indecent exposure. Those who oversee the Appalachian Trail, where hikers making the trip from Georgia to Maine often observe the tradition, also are discouraging outdoor nudity.
"It's just rude," said Brian King, spokesman for the Appalachian Trail Conservancy in Harpers Ferry, W.Va. "People are out there hiking with their kids and families, and there are Girl Scouts and Boy Scouts."
Authorities admit that there are so few hikers who bare all, even on the first day of summer, that they don't consider it a major problem.
"It's rare, probably because we have a lot of remote territory out there where one would not be detected," said Capt. Woody Lipps of Virginia's George Washington and Jefferson national forests, through which parts of the Appalachian Trail run.
Naked hiking enthusiasts like Warren, Pa., resident Andrew Williams defend the practice.
"There's no way to explain it until you experience it," said the 28-year-old machinist. "It's not about being lewd and crude and all that. It's just enjoyment."
And, they say, they aren't out to shock people.
"I go out of my way to avoid being seen," New Orleans software engineer Shane Steinkamp, 40, wrote in an email. "I value the freedom to be able to walk in freedom, but I also accept the responsibility that I should not surprise folks who may take my enjoyment of nature in the wrong way."
The Associated Press contributed to this report.