The call came after it was revealed 1300 RACV patrols were called out to assist people and pets across Victoria in the last 12 months.

Ballarat Police endorsed the message after attending two reported incidents this week.

RACV chief engineer, vehicles, Michael Case said the figure equated to more than three rescues a day.

"It's a number (we) would like to see reduced substantially," Mr Case said.

Mr Case said parents who were tempted to leave children in vehicles while visiting shopping centres must think again.

"In the past we have heard of horrifying stories where children ... have been locked in cars while parents attended to other business," he said.

"It's quite easy to think 'I'll only be gone for a few minutes,' but it's unbelievable how quickly the temperature can rise inside a car."

Mr Case said the interior temperature of a vehicle could rise by as much as 40 degrees Celsius in just 15 minutes.

He said children could suffer heatstroke, dehydration, or even die as the mercury neared the lethal 60 degree mark.

Mr Case said leaving a window open a few centimetres would not ensure protection.

"It won't reduce the car's interior heat by very much," he said.

Mr Case said families who placed their children most at risk were owners of modern, round-shaped vehicles.

"They're more aero-dynamic, which helps the performance of the vehicle. But the increase in the amount of glass exposed to the sun means the car heats up faster," he said.

Meanwhile, Ballarat Police Acting Inspector David Hermit urged people to be vigilant with temperatures forecast to soar above 30 degrees today and tomorrow.

"Don't leave your children unattended," he said.

Anyone who sees a distressed child or pet locked in a car should call 000 or 53366000.