It had already dropped well below zero degrees Fahrenheit by the time Sergei arrived at the white medical van near the train station.
A threadbare coat did its best to block the bitter wind. Sergei tugged on a wool cap as cold gusts slammed into gaps of exposed skin. But that wasn't his biggest concern. Night was coming soon and his feet were freezing. He'll need them to keep moving if he wants to survive until morning.
Sergei joined dozens of others crowding around the van. They are among this frozen city's most vulnerable population: the homeless, and they fear freezing to death every night.
Some of them came for the a warm meal, others for medical attention. Sergei opted only for a pair of warm socks.
Nearby another man named Gennady clutched a bag of medicine he picked up.
He has to be careful. Recently a friend was among the estimated 220 Russians who have died during the past three weeks, the longest deep freeze here in 75 years. Temperatures have fallen as far as -14F on some nights. Few days have risen above 2F.
Gennady's story is sad, but not unique.
He arrived in Moscow in 1997 from his native Belarus to find work in construction.
"I got a job and everything was great," he recalled.
When new bosses took over the company, however, anyone without a Moscow residence permit was fired. He survived for a while on odd jobs remodeling homes.
But one day he says he was beaten up by a group of drug addicts and was in the hospital for two and a half months. During the scuffle he lost his registration papers, making finding legitimate work impossible in a country where a passport is required for even simple tasks like picking up dry cleaning.
From there it was not long before he found himself on the streets.
Many other men who came to the van that night had similar stories. Most migrated to the Russian capital from the countryside or from neighboring countries in search of work. Many who were lucky to find a job faced discrimination from employers. Some struggled with addiction.
Their plight on the streets is compounded during the long, harsh Russian winter. The cold lasts six months a year and the darkness lasts up to 17 hours a day.
"We try to survive," Gennady said.
During the day he rides the subway for hours. It's one of the few warm places where he can sleep. At night he wanders the streets to fight off frostbite after he and other homeless people are kicked out of the stations.
Sunday was Gennady's 43rd birthday.
After a half dozen years providing medical care to Moscow's homeless, Dr. Elizaveta Glinka, or Dr. Liza as she is known, has seen everything. The most common injuries are frostbitten extremities and burns from unsafe heaters.
The worst, she says, are the frozen bodies she and her fellow volunteers find.
Every day she sees homeless patients in her clinic, part of a charity she runs called "Just Help." Every day about 100 people come there for food. A couple times a week she and her team take the van out to reach more people in need.
As men and women crowded around her van she doled out medicine, clothing, advice, and a hopeful smile. This was a good day. Someone donated a jar of caviar and she was able to spoon out some of the delicacy to the needy.
"This time of year there are a lot more people than in the summer. Now there are lots of people," said Nikolai Belikoff, one of the volunteers.
One of them is another homeless man named Alexander, who came to the van that frigid night in search of medicine and a warm meal.
Moscow's Homeless Walk All Night to Survive Frigid Temperatures
He was a welder, but he said one day his employer took his identification documents to issue work permits. He never saw the man or his papers again.
He explained that he cannot get into the city's homeless shelters at night because they are reserved for people from Moscow. He also knows people who have died from the cold, but so far he hasn't gotten frostbite.
"Thank God, not yet," he said.
Alexander comes to the mobile clinic most Wednesdays for warm food and medicine. He says they've help keep him alive.
Stanislav is luckier than most. He has been going to the same building entrance every night for two years. They don't kick him out, he explains, because he doesn't cause any trouble.
"They know me there. They don't touch me," he said.
Others, he said, are expelled from public buildings when they close for the night. He knows homeless people who disappeared after a particularly cold night.
As Dr Liza saw her last patient for the night -- a man who wanted her to inspect his ear -- Nikolai and the other volunteers packed up the van.
The crowd dispersed and Sergei, his new socks still in hand, walked off into the night.