Animal welfare authorities usually advise that a car with a dog inside must be parked in the shade, windows lowered at least 2cm and drinking water made available.
Ms McSkimming said the Otago SPCA still received many complaints about dogs in hot cars throughout the South, and pets should be left at home to keep them safe on hot days.
"Leave them at home is the best thing you can possibly do," she said.
The SPCA received more than 100 complaints each year in Dunedin alone.
"In Dunedin we can get up to five or six [complaints] a day.
There had been no recent deaths but "some close calls".
If the weather was really hot, letting car windows down just a small amount while visiting a supermarket would not provide adequate air flow — "it doesn’t give them a bit of relief".
"They get extra hot in the cars," she added
"You think it’s only 20degC outside but it can soon be 35degC-40degC in the car," she warned.
Stronger animal welfare regulations, which took effect in 2018, give animal welfare inspectors the power to fine people for leaving dogs in hot vehicles.
The SPCA and the Ministry for Primary Industries can fine those involved with a dog getting heat-stressed in a vehicle.
Before 2018, inspectors could take action under the Animal Welfare Act only if a heat-stressed dog died.
Anyone with concerns for a dog in a car should call police or SPCA, Ms McSkimming said.
"We talk about it every year, but we still seem to be getting a lot of hot dogs in cars."
Acting Sergeant Richard Kupenga, of Dunedin, also urged motorists to "never leave your pets unattended in a car because heat can kill".
"Six minutes is all it takes for a dog to overheat in a hot car and you could lose your best friend forever," he said.
"If you have to leave your pet for a short time, leave them secured in a safe area with access to shade, water and ideally with a responsible person."
