Napa police posted a picture on their Facebook page of the dog after the rescue.
Police responded after they got a call from someone who noticed the dog inside a car in the parking lot of the South Napa Marketplace. A thermometer showed the temperature inside that car to be 136 degrees.
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Officials said the dog's owner was shopping at the time.
The dog is under the care of a vet, and police are asking dog owners to leave their pets at home when it's this hot.
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Click here to read more stories about pets and children being left in hot cars.