Dramatic video obtained by ABC Atlanta affiliate WSB shows shoppers at the Georgia Walmart spot the little boy inside the parked car.
When officers raced to the scene in McDonough, outside Atlanta, they found the little boy in a locked car which was turned off and with the windows rolled up, according to the McDonough Police Department.
Officers forced their way into the car, removing the 2-year-old, said police. Video also showed the concerned citizens and officers comforting the little boy once he was rescued.
The 2-year-old was taken to Henry Piedmont Hospital and later released, said police.
The boy's father, Christopher Urgent, was arrested for cruelty to children, according to police.
The temperature climbed to 86 degrees near McDonough on Tuesday. With sunny skies, the inside of the car could have heated up to 104 degrees in just 10 minutes, according to ABC News meteorologists.
It's not clear how long the boy was locked inside the car, according to police.
Amber Rollins, director of the national nonprofit KidsAndCars.org, said the citizens' and officers' "quick action quite literally could have been the difference between life and death for this young child."
"If you see a child or animal alone in a car, do something," Rollins told ABC News. "If they are in distress, you need to get them out immediately and begin to cool them."
Hot car deaths reached a record level last year with at least 52 children killed, according to KidsAndCars.org.
ABC News' Max Golembo and Sam Wnek contributed to this report.