Volunteers will hit the city’s alleys, streets and CTA lines Tuesday night to ask people who are sleeping outside or on trains and buses if they have a place to go.

If those people say no, they’ll be counted in Chicago’s biennial “point-in-time” homeless census. The count happens in January because on colder nights, more people are likely to check into shelters – where they’ll get counted automatically – leaving fewer people to count elsewhere. 

This one-night census can’t establish the total number of people experiencing homelessness, but it does provide data that’s used by the federal government to parcel out funding for anti-homelessness initiatives around the country.

Tedd Peso of the Night Ministry, an agency that provides services to homeless youth, remembers the last count.

“It was cold, but it was not this cold, and I remember there was snow on the ground,” he said. “But tonight’s gonna be a cold night.”

But who’s still outside on a night that’s predicted to be 8 degrees with a windchill below zero?

“You and I may think when it’s 1 degree or 5 degrees out, why wouldn’t somebody wanna go into a warming shelter?” Peso said.

During two previous counts, Peso said he’s learned that for some people, a shelter full of strangers may feel even less safe than the streets. For others, mental health issues make it harder to get there.

“Sometimes people just don’t have the cognitive understanding of how to find out the information to go to a warming center or go to a shelter,” Peso said.

Chicago’s 2011 count found more than 6,500 people in shelters or on the streets, and of those, one in five was severely mentally ill.

But the count is just a snapshot of one night. Estimates of the number of people who are homeless range much higher, from 21,000 to more than 100,000. These larger numbers include families who have lost their homes and are now living doubled-up with friends or relatives.

Even some of the higher numbers may not include minors if they’re not with their families. The Night Ministry estimates that on a given night, there about 2,000 unaccompanied youths on the streets. Citywide, there are about 300 shelter beds for young people.

Peso said for youths who are out there alone, it may be safer for to avoid revealing they’re homeless.

“For a person who’s on the streets, that might be their way that they survive is by telling people that they have a place to stay tonight,” he said. “That’s their survival is not letting people know they’re homeless.”