The baby girl was rescued by a construction worker named Eric Asher and his fiancée.
Eric Asher, 43, shared photos of his ordeal in Canton, Ohio on social media, and it provoked outrage from shocked viewers.
The good Samaritan says he saw a man and a woman passed out on the ground of a parking lot as he drove past on Friday. He then noticed a baby girl in a car seat. Temperatures had reached 88F (31C) and the girl was sweating. He then rescued the baby from the open car and gave the child water as a bystander called 911. Soon, emergency services rushed to the scene.
He told Inside Edition: “We were driving down the road and I looked over to my right and I saw the male and female laying on the ground. We later saw that they were purple. The child was covered in sweat. We gave the baby some water – that was our priority.”
Mr Asher said the child’s mother later rang him to thank him for saving their daughter. She told him they were heroin addicts and had relapsed after being clean for two years, he said.
The child is now being looked after by a relative.
Court records seen by MailOnline show the parents have been charged with endangering a child and released on $1,000 bonds.