York Regional Police say officers were called to the Vaughan Mills Mall at about 2 p.m. Sunday after a passerby saw the unattended child sleeping in the back seat.
Police say the windows of the vehicle were left slightly open but that the temperature outside the vehicle was more than 30 C and the child was showing obvious signs of extreme heat exposure.
Officers forced down the window and rescued the child, who was found to be hot to the touch, her skin red and her hair drenched with sweat.
A Toronto man was arrested after police say he returned to the vehicle about 30 minutes after the girl was discovered.
He's charged with leaving a child unattended.
The girl was taken to hospital as a precaution and was released into the custody of her mother.
Police remind the public that children and pets can quickly become overheated and dehydrated if left unattended in hot vehicles, which can result in serious injury or death.