Officials said the car was not one the woman typically drove, which may have led to her accidentally locking the vehicle while putting the baby and other personal items inside.
Lincolnwood Fire Department Capt. Dean Friedlund said firefighters responded to a report of an infant inside a 2012 Infiniti SUV near the Olive Garden at Lincolnwood Mall on Friday afternoon.
He said the baby was inside the vehicle for about 10 minutes, and temperatures inside reached 112 degrees. A tow truck operator was called to open the locked car.
The baby was not injured but was transported to St. Francis Hospital for evaluation.
Infants are especially vulnerable to heat exhaustion and heat stroke, one doctor told CBS 2.