The RSPCA is investigating the death of a dog which was trapped in a car for two hours as Perth’s temperature nudged 30 degrees Celcius yesterday.

The male mastiff was left inside a Holden Astra on Fletching Street in Balga in the afternoon.

Facebook user Amy Middleton said concerned onlookers opened an unlocked door to free the dog but it later died.

Camera Icon The dog which died in Balga yesterday. Credit: Amy Middleton/Facebook

“A group of strangers came together as a team, one man carrying him from the car to somewhere cooler so a woman who pulled up as well to help (and happened to be a vet nurse) performed CPR,” she wrote.

“Everyone did what they could but unfortunately it just wasn’t enough, we lost him and everyone there at that moment was beyond sorry to that animal.”

The RSPCA was also called but inspectors arrived to find the dog had perished from the heat.

In a statement today, RSPCA WA said the temperature inside a parked car yesterday could have hit 50C and could have killed a dog within six minutes.

Chief inspector Amanda Swift said she was “deeply saddened” by the dog’s death.

"Dogs dying from being left in parked cars is not acceptable – it’s an offence; and it’s completely avoidable. There really is no excuse for this to be happening,” she said.

"We often hear excuses like they were only going to be five minutes, or it’s not really that hot today. It’s not good enough.”

The RSPCA confirmed it is also investigating a case where two other dogs survived being locked in a car near the Belmont Shopping Centre in Cloverdale yesterday.

The dogs’ owner arrived before inspectors arrived.

Ms Swift said people who left their dogs in cars on a hot day could face a fine of up to $50,000, five years’ in prison and a lengthy ban from owning an animal.

Anyone who sees a dog locked in a car on a hot day is asked to note down the car’s registration, contact the RSPCA’s cruelty hotline on 1300 278 3589 and keep an eye on the dog until help arrives.

The RSPCA advises those who see dogs in hot cars near shopping centres to contact centre management to page the owner of the vehicle.