Bob Glennon eyed the front door to Miriam’s Kitchen with trepidation. As the daily breakfast service for the homeless was about to begin at 6:30 Tuesday morning, after one of the coldest nights in two decades, Glennon was anxious about who would show up. And what it might mean if they didn’t.

Despite his best efforts as a social worker, he knew that some of the regulars, some of the estimated 400 chronically homeless in the District, had chosen to sleep outside in the frigid weather rather than go to an emergency shelter for the night, risking frostbite, hypothermia, exposure and worse.

Glennon had warned them about the unusual cold snap. He had written advisories on the chalkboard in the dining room and made sure everyone had the emergency shelter hotline number.

Still, some of the regulars had brushed him off. “We’ll be all right,” he recalls them saying.

He waited to see if they were right.

“Some of them just have a real street warrior mentality,” Glennon explained. “That sense of ‘This is just what we do.’ ”

Theirs, he said, is a completely different definition of “normal.”

They have their camping spots, their routines. They know how to layer their clothes, stick hand warmers in their shoes and roll up in extra blankets. They know to lay cardboard on top of concrete, asphalt or grass to keep warm. And many of them prefer their freedom and solitude in the cold, whether under tarps on the street or under bridges, to the crowds and chaos of emergency shelters.

Glennon calls them “campers.” And for 15 years, he has worked to get them to come in from the cold. Or at least make sure they’re relatively safe and warm when they don’t.

On Tuesday morning, the line that usually stretches down the block outside the Miriam’s Kitchen dining hall on Virginia Avenue NW was noticeably shorter. He hoped that meant that people had chosen to go to shelters, which were staying open all day rather than regularly closing in the morning.

As the doors opened and people began to load their plates, he watched carefully, making a mental note of the handful of regulars who had come in.

“Some of these folks stay outside in groups, and they look out for each other,” Glennon said. “But the people who are on their own, those are the ones I worry about.”

Studies have found that homeless people die younger than the general population. The biggest killer is untreated medical conditions, but exposure, in extremely cold or hot weather, also takes lives.

In his years as a social worker for the city’s then-Department of Mental Health (now Department of Behavioral Services), he was responsible for deciding when to call for an “FD-12,” or an involuntary commitment to a warm place when a person is judged to be a danger to themselves or others.

“We’d see people out in weather like this in T-shirts, saying that God had given them a special warming ability,” Glennon said. “For a FD-12, you have to be able to tie a person’s mental illness to their dangerous behavior.”

And if campers know how to keep warm and refuse to come in, all he can do is worry until they show up for breakfast.

Glennon circulated through the tables of homeless diners. While he wanted to talk weather, the campers wanted to talk about jobs, or substance-abuse treatment programs, as if it were just another day.

Jeff Gilliam, 53, typically lives on the streets in a group of four. But he admitted he was too cold to stay outside and asked to stay with a friend.

“He might ask me to leave; it’s beginning to get a little uncomfortable,” Gilliam said.

Across the table, a young man who asked not to be identified, said he lived with a group of six under a freeway bridge and they had no plans to go to hypothermia shelters, although they appreciated the shelter hotline van checking up on them and dropping off extra blankets.

“Our camp is cool. We even have a fire. We cool there,” the young man said. “We have sleeping bags. We can get into the bridge and out of the wind. It wasn’t that bad last night.”

By 8 a.m., as the breakfast service ended and the cleanup began, Glennon noted with relief that just about all the regulars had made it in. One regular didn’t.

A woman with a blond ponytail took Glennon down the block and across the street. On a freeway overpass, on the sidewalk just under a concrete retaining wall, the woman patted a crumpled blue tarp and called to the woman bundled up inside.

“I’m all right,” a voice called from the depths.

Glennon walked back to the dining room and began persuading yet another young street warrior to stay at the shelter for the frigid night yet to come.