CANNON BALL, N.D. — So far, the hundreds of protesters fighting the Dakota Access pipeline have shrugged off the heavy snow, icy winds and frigid temperatures that have swirled around their large encampment on the North Dakota grasslands.

But if they defy next week’s government deadline to abandon the camp, demonstrators know the real deep freeze lies ahead, when the full weight of the Great Plains winter descends on their community of nylon tents and teepees. Life-threatening wind chills and towering snow drifts could mean the greatest challenge is simple survival.

“I’m scared. I’m a California girl, you know?” said Loretta Reddog of Placerville, California, a protester who said she arrived several months ago with her two dogs and has yet to adjust to the harsher climate.

The government has ordered protesters to leave federal land by Monday, although it’s not clear what, if anything, authorities will do to enforce that mandate. Demonstrators insist they will stay for as long as it takes to divert the $3.8 billion pipeline, which the Standing Rock Sioux tribe believes threatens sacred sites and a river that provides drinking water for millions of people.

The pipeline is largely complete except for a short segment that is planned to pass beneath a Missouri River reservoir. The company doing the building says it is unwilling to reroute the project.

For several months, the government permitted the gathering, allowing its population to swell. The Seven Council Fires camp began growing in August as it took in the overflow crowd from smaller protest sites nearby. It now covers a half square mile, with living quarters that include old school buses, fancy motorhomes and domelike yurts. Hale bales are piled around some teepees to keep out the wind. There’s even a crude corral for horses.

The number of inhabitants has ranged from several hundred to several thousand. It has been called the largest gathering of Native American tribes in a century.

Increasingly, more permanent wooden structures are being erected, even though the Army Corps of Engineers considers them illegal on government property. The Standing Rock Sioux insist the land still belongs to their tribe under a nearly 150-year-old treaty.

Nate Bison, a member of South Dakota’s Cheyenne River Sioux, came to the camp after quitting his job in Las Vegas a week ago. He said he intends to stay indefinitely, a prospect that may cause him to lose his house in Nevada.