The homeless are among the most vulnerable as dangerous and brutally cold wind chills target the Midwest cities Wednesday.
In Chicago and Minneapolis, where schools are shuttered and everyone is urged to avoid the outdoors, warming centers and buses are available for homeless residents.
Wind chills clocked in at minus 52 degrees Wednesday -- a recipe for frostbite.
"We're deploying warming buses to assist homeless residents, adding shelter beds to accommodate those in need," Chicago Mayor Rahm Emanuel tweeted.
Mada Leanga, who works with a Chicago organization which provides housing and healthcare for people with mental illness or substance abuse problems, came out in the bitter Wednesday cold to check on the homeless.
"No matter how many layers you put on top you're freezing because of the moisture," she told ABC News. "A lot of people were sitting under a lot of blankets but the blankets were frozen."
She said the warming centers aren't enough, and some people, especially those with mental illness, don't have many options.
Leanga said she's seen so many Chicagoans helping the homeless in their neighborhoods, from offering clothes and coffee to a place to stay.
Leanga said she and her colleagues give away blankets and hand-warmers, but at this point their goal is to get the homeless safe inside warming centers.
Over 5,000 people were homeless in Chicago last year, according to data released by the city, The Chicago Tribune reported.
Here are links to warming center locations in the Chicago and Minneapolis:
ABC News' Alex Perez and Andy Fies contributed to this report.