Paramedics have been called to more than 200 cases of children locked in cars across Victoria since the start of the year, the ambulance service has revealed.

Victorians face prison terms of up to six months and fines of almost $3,700 if caught intentionally leaving children under the age of 12 unattended in a car.

Ambulance Victoria Group Manager Brett Drummond said it was frustrating that the message was not getting through.

"There's been a significant amount of media coverage this summer to warn against the dangers of leaving children in cars," Mr Drummond said in a statement.

"On top of that, the penalties for leaving a child unattended have been increased.

"Despite that, people are still willing to gamble with their children's lives.

"It's never okay to leave a child in a car, no exceptions, no excuses."

Triple-0 calls to children locked in cars: Metro East/South: 77

Metro East/South: 77 Metro West/North: 73

Metro West/North: 73 Barwon/South West: 18

Barwon/South West: 18 Granmpians: 12

Granmpians: 12 Loddon Mallee: 4

Loddon Mallee: 4 Hume: 9

Hume: 9 Gippsland: 11

Gippsland: 11 Total: 204

Last year more than 1,100 children were rescued from inside locked cars by paramedics.

Ambulance Victoria said testing found that on a 29 degrees Celsius day, the inside of a car would reach 44C within 10 minutes and 60C within 20 minutes.

Mr Drummond said with warm weather forecast for the weekend in Victoria, children's lives were at risk.

"The mercury will be in the 30s in Melbourne and into the 40s in the north of the state over the next week," he said

"We have seen children die in hot cars in the last few years – just don't take the risk."

He said people in the eastern and southern suburbs of Melbourne were the worst offenders, with 77 calls made to triple-0, followed by the north and west of the city, with 73 call-outs.

"Some of the triple-0 calls result from people who have accidentally locked their keys in the car with their child," he said.

"Hold onto your keys until you are ready to hop into the car as well."