Emergency crews responded about 11:50 p.m. to the blaze that started in the first floor of an apartment building in the 9000 block of South Harlem Avenue, Bridgeview Fire Department Battalion Chief Dave Lis told reporters at the scene.
Firefighters rescued one family that was trapped in the unit, and the fire was struck out by 12:30 a.m., Lis said.
One woman was taken to an area hospital in "stable" condition to be treated for smoke inhalation, Lis said.
The Greater Chicago Red Cross was assisting 15 adults and three children displaced by the fire, according to the organization's Twitter feed. The cause of the fire is under investigation.
The dangerous cold temperatures made things difficult for firefighters.
For a lot of us, it is challenging to stay warm, but for firefighters it makes everything more difficult because the weather makes everything freeze. They encountered frozen hydrants.
Residents had to rush into the cold weather, some still wearing pajamas and blankets wrapped around them. Residents were able to step into a business across the street to stay warm while fire crews fought the blaze.
The Sun-Times Media Wire contributed to this report.