As temperatures in Victoria are set to soar, authorities have warned parents not to leave children in cars alone after an increase in triple-0 calls.

Emergency crews rescued 1,433 children from cars in the 12 months to the end of August, a 23 per cent increase in calls on the previous year.

Families and Children Minister Jenny Mikakos said there were no excuses for leaving children inside hot cars.

"Tragically, eight incidents have involved children being taken to hospital," she said.

"370 babies have been rescued, a 50 per cent increase on the year before, and we have had children who have died from being left in a vehicle."

Children under the age of four made up 88 per cent of calls to emergency services.

Ambulance Victoria said its tests found that even on a 29-degree-Celsius day, the inside of a car could reach 44C within 10 minutes, and 60C within 20 minutes.

Ms Mikakos urged parents to take children with them when Christmas shopping.

"They might think they might be going in to the shops for a couple of minutes [but] they don't know what's going to happen, whether they're going to be detained whilst they're there," she said.

"You are putting your child's life at risk if you leave your child unattended, even for five minutes in a car."

She said the rise in calls to emergency services could be due to community awareness.

"We know there is more community awareness about risks, so people are more likely, when they see a young child left in a vehicle, to the ambulance and call police," she said.

Ambulance Victoria said not all calls were made as a result of children deliberately locked in cars, but in many cases cars had been accidentally locked with children inside.

Victoria is set to experience high temperatures over the next few days, including a top of 39C on Saturday.