"The caller advised they thought the dog had been there for around an hour," she said.
Police tracked down and contacted the registered owner of the car and told him to get back to the car and help the dog. Meanwhile, bystanders trying to find the owner on the beach had also tracked him down, the spokeswoman said.
Police arrived about the same time as the owner who unlocked the boot. The puppy was barely conscious and suffering from extreme heat stroke, she said.
"The officers assisted with trying to get the dog cooled down by placing it under a cold outdoor shower, as the dog appeared to be very unwell."
The puppy was also covered in ice in an attempt to cool it down, and it was rushed to an after-hours vet.
Mount Maunganui Veterinary Hospital vet Dr Eoghan O'Connor said the puppy was unconscious, having seizures and was close to death when it was brought to the clinic.
He and veterinary nurse Rebekah Van de Pas carried out a range of measures to revive him, which included raising his body temperature because he had been "over-cooled" under a cold shower, after being taken out of the car.
"We did everything we could to revive him, and slowly but surely he started to come around ... it was a heartwarming moment."
The dog had since made a strong recovery and was now displaying signs of a playful personality.
"It's remarkable he survived," Dr O'Connor said.
He thanked two bystanders, in particular, who went above and beyond to help the puppy.
SPCA communications manager Jessie Gilchrist said SPCA inspectors were undertaking a full animal welfare investigation.
The owner had surrendered the puppy to the care of the vet and the SPCA.
A Tauranga City Council spokeswoman said the incident was "a very distressing situation".
Don't leave your dog alone - SPCA's plea
On a warm day, the inside of a car heats up very quickly. On a 30C day, the temperature inside a car can reach 39C in less than 5 minutes and in 30 minutes, it goes up to 49C. This occurs even in the shade and if windows are open.
A normal dog's body temperature is around 38.5C. Dogs only sweat a small amount through their paws and rely on panting to cool down. In a hot car, even with the windows slightly open, panting is not enough to keep a dog's body temperature within a safe range.
Source: SPCA
