A dog has died after being left in a car in Perth's afternoon heat while two others have been placed at similar risk.
The male mastiff was unable to be saved after being shut in a vehicle for about two hours near a shopping centre in Balga on Wednesday.
Members of the public spotted the distressed animal and reported it to RSPCA WA inspectors but it was too late.
Separately, police were alerted to two dogs in a car in Cloverdale but the owner returned before inspectors arrived.
An investigation into both incidents is underway.
RSPCA WA chief inspector Amanda Swift said it was a cloudy 27C in Perth but the temperature inside the cars could have been double.
She said a dog could suffer heat stress and die within six minutes and parking in shade or underground with windows down offered little relief.
"I'm deeply saddened and frustrated by the loss of an innocent dog yesterday, who died in horrific circumstances as a result of people's negligence," Ms Swift said.
"Dogs dying from being left in parked cars is not acceptable. It's an offence and it's completely avoidable.
"I can't understand why the message isn't sinking in and why dog owners continue to put their pets' lives in danger."
Since December 1, RSPCA WA has received 132 reports of dogs in hot cars.
Anyone who leaves a dog in a car faces a maximum penalty of $50,000 or five years' imprisonment and can be banned from owning an animal for a period.
