Blanketed homeless people catch the eye of a bundled-up pedestrian on K Street NW in the District on Dec. 29, 2017. (Michael S. Williamson/The Washington Post)

In weeks like this one, when temperatures sink into the teens, city officials do just about everything they can to get the roughly 900 people living on the streets of Washington inside. They open additional shelters. They partner with nonprofit organizations, doubling the number of people searching for the homeless in Metro stops, in parks, in tent encampments along busy intersections. They leverage relationships with homeless people that have taken months, if not years, to build.

For the most part, it's successful. As of Friday morning, the parks and Metro stops of downtown Washington — normally populated with the homeless — were just about vacant.

But not of everyone. There were still a few people like Dion Cruz, a curly haired 34-year-old who was rustling beneath a heap of blankets, as dawn came over Washington on Friday and he woke from one more night spent on K Street NW. His eyes opened, and his hands went to a face that was peeling and picked over. "Look at my face," he said. "The shelters aren't clean. They're infested with bugs. I went there for a week, and woke up in a rash. I was there on Monday. I haven't been back."

Cruz, who is choosing to sleep on concrete during one of the coldest sustained chills to grip Washington in years, represents one of the most vexing and in­trac­table issues facing government officials and organizations that serve the homeless. Some people simply don't want to come inside. No matter how cold it is. Or wet. Or high the danger of remaining outside.

The number of people like Cruz in Washington, whom the District refers to as unsheltered single adults, has grown dramatically over the past five years, from 512 to 897, even as a years-long surge in homeless people in Washington has begun to subside. This comes as homeless people across America are increasingly turning away from established shelter systems, instead opting for so-called tent cities and other homeless communities.

According to a report published this month by the National Law Center on Homelessness & Poverty, the annual number of unique homeless encampments reported in the media rose 1,342 percent between 2007 and 2016, from 19 reported encampments to 274. "This increase in encampments reflects the growth in homelessness overall," the report said, "and provides evidence of the inadequacy (and sometimes inaccessibility) of the U.S. shelter system."

Dion Cruz, above, shivers on the sidewalk. Brutal wind chills are expected this weekend in the Washington area. (Michael S. Williamson/The Washington Post)

The stakes are ratcheted up even more now, with near-zero wind chills expected to move in on Sunday and Monday. Hypothermia was the cause of death for four people in fiscal years 2016 and 2017, according to city records. There hasn't been a recorded hypothermia death this fiscal year.

"We're most concerned," said Christine Elwell, director of outreach for Pathways to Housing DC. "The weather has changed so precipitously. Just a few days before Christmas, it was 60 degrees, and we're worried about people's abilities to plan on really short notice. . . . One death on the street is too many."

Especially worrying, she said, are those with mental-health issues so profound that they can't be trusted to decide for themselves whether it is safe enough to remain outside. Or other homeless people may have health issues that could be exacerbated by cold weather, or start drinking as a method of staying warm.

That's David Carter, 29, who woke Friday morning on some steps near a construction site at the corner of 15th and L streets NW. He has been homeless for the better part of a decade, and has come to hate the shelters — which he perceives as having endless rules — so on Thursday night, he did what he has done many nights. He drank until he felt warm and, confident he wouldn't wake in the middle of the night, went to sleep.

Come morning, he was walking the streets, wrapped in a blanket a city worker had given him, thinking that the night he had just spent had been terrible, but not as terrible as it would have been had he been inside a shelter. "It's like jail," he said.

Carter, who suffers from depression and believes he may have schizophrenia, understands certain things about himself. He knows he drinks and smokes, and doesn't want to stop. He knows he doesn't take directions well, and can clash with people. And he knows he has made enemies among the homeless, people whom he would rather not see, people he probably would see at a shelter. So instead, to get warm, he went to the McDonald's at the corner of 13th Street NW and New York Avenue — the "homeless McDonald's," he called it — where he would normally find many others like him, but today only noticed one, a bedraggled man begging for money, whom he ignored.

Carter took off his blanket, placed it near the door, sat at a booth and said that he had only been to a shelter twice in three years. He went once in 2014, but the sign-in sheet that asked for his name had made him suspicious. And again last winter, when a van rolled to a stop before his bedding of blankets and he was told that he would die if he stayed outside. So Carter went to the shelter, but became so anxious that he left the next morning, swearing he wouldn't return unless there was a true emergency.

All he needed to make it outside, he believed, was his blanket, which was now being thrown into the trash by a McDonald's employee.

"Hey, that's my blanket, ma'am!" he said. "That's my blanket!"

"You cannot leave it here," the employee said, pushing it into the wastebasket.

"I need to sleep on that, ma'am! Don't throw it in the trash."

He got up, retrieved his blanket, wrapped himself up again, then headed back into the cold. Three blocks away, Cruz was still covered by his own blanket as morning got on toward noon.

There, a man in warm-looking leather boots, carrying a cup of coffee and a sandwich, was stopping in front of Cruz's blankets. "Hello?" the man said, handing Cruz the meal. "Hello!"

Cruz lowered a blanket to show his face. He silently accepted the gifts, then dropped his head again beneath the blankets. It still wasn't time to face the cold, not yet.