The cold comes as the city and suburbs recovers from last week's historic blizzard.
The city is asking people to check on the sick, the elderly and those who live alone.
Landlords are required to keep temperatures at 68 degrees during the day and 66 degrees at night. Tenants can call in complaints to 311.
The city is opening warming centers throughout Chicago. People can also go to libraries, police stations and fire stations for temporary protection from the cold.