Children die in hot cars.

It seems like a simple message, but a spate of incidents interstate and constant reminders from emergency services, health professionals and children's advocates reveal a telling sign about children's safety.

Canberra is tipped to be the hottest major city in Australia for Sunday and Monday with the mercury rising to 37 degrees.

As residents swelter through the heatwave, parents and caregivers need to be vigilant about not leaving children in hot cars.

A new warning with an old message has been issued by Kidsafe ACT and the ACT Child and Young People Death Review Committee.

The groups are urging Canberrans to focus on keeping their children safe particularly on hot days in cars.

Heads of both groups have come together after concerns that parents aren't heeding the message.

"Tragically in the past children have died from being left alone in cars," their media release reads.

"Recent media reports highlight that parents and caregivers are still ignoring warnings about the risks of serious heat related injuries or death to children who are left unattended in cars during hot weather."

Their concern is that "all too often, the child is forgotten whilst the driver is under great stress".

Has our country come to a time when focusing on anything else is more important than the safety of our children?

NSW police are also concerned about the issue, but they expanded their warning, saying it's not just children that aren't safe in hot cars.

"It's not only an offence for children or pets to be left unattended in a vehicle, it can be deadly," the spokesman said.

"It can be just as dangerous to leave the elderly and disabled members of the community in cars during days of extreme heat."

Common sense would surely prevail in these situations, but it seems not for everyone, hence the need for constant reminders.

So, let's hear it again: children are not safe in hot cars. Remember and heed the warning.