The baby, Kimberly James, who was just 14 months old, is believed to have been in the car for in excess of three hours in the town of Miramar near Miami, Florida. Temperatures at the time were reaching over 100 degrees Fahrenheit (38c).
Her father, Odane, who is thought to be a pastor, found her lifeless body when he returned to the vehicle after taking part in the morning service at the Holiness Born Again Church.
Other parishioners fought desperately to revive the infant, but she was pronounced dead after being taken to hospital.
A police spokesperson, Tania Rues said: 'Toddler Kimberly was found at about 3.15pm on Sunday after services finished at the church. The girl's father Odane returned to his car and discovered Kimberly inside'.
Witness Guy Italien, who owns a restaurant next door to the church, told the Miami Herald: 'I saw a police officer come here. Then many, many more.'
He said he went outside and saw a police officer holding the motionless baby with hordes of people crying and screaming around her.
The group Kids and Cars say that Kimberly is the 49th child to die in the U.S. this year after being left in a hot car.
What do you think?
Have you ever left your child alone in the car?