The Rotorua SPCA has been called out several times to dogs left in hot cars this summer, however, the number of cases has not increased, prompting hopes the animal charity's safety messages are getting through.
Manager Sue Kinsella told the Rotorua Daily Post the number of cases was "no more, and no less than previous years".
She said she had anticipated extra callouts during this week's heatwave, but that didn't eventuate.
"Hopefully the message is getting through that pets cannot be left in cars in summer even for just a few minutes."
She said many calls about dogs left in hot cars went directly to the police.
According to the SPCA, on a 30C day, the temperature inside a car can reach 39C in less than five minutes and 49C in 30 minutes, even in the shade and with windows open.
Excessive panting, breathing difficulties, weakness, or drooling are signs of heat exhaustion in dogs.
Overweight dogs, dogs with short or flat noses, long-haired breeds, puppies, old dogs and sick dogs tend to struggle more in the heat.
The Ministry for Primary Industries is also reminding animal owners of their "special responsibilities" during a heatwave.
National animal welfare co-ordinator Dr Wayne Ricketts said owners needed to be "making sure animals have enough water, are in shade and there is good airflow".
"It's all good common sense stuff, yet every time we have a heatwave MPI hears of animals being left without these things."
Caring for dogs in summer heat
• Hot pavements can burn the pads of paws, leaving them sore, blistering and red
• Fair-skinned or light-haired dogs may need pet-friendly sunscreen on their ears, nose, and stomach, to prevent sunburn
• Exercise dogs early in the morning or in the evening in cool shady areas, with water available, to prevent overheating