And there's an even worse warning from insurers, which often don't pay out claims in such cases.

At 8.30am in Fadden, a resident started the engine on the family's VW Golf in the driveway, turned the windscreen heater fan on full blast, and then walked back inside.

In the time it had taken for him to pick up his one-year-old son and carry him outside to put him in a car seat, the car was gone.

The theft happened in less than one minute.

"It happened so fast; it was unbelieveable," the owner said.

"It was a pretty slick operation; they [the thieves] must have been driving around just watching and waiting for that opportunity.

"It couldn't have happened any other way."

The Golf was the second car in Tuggeranong to be stolen exactly the same way around the same time. A Honda was stolen while sitting idling and defrosting in a Wanniassa driveway.

Meanwhile, across the border in Jerrabomberra, another car was stolen the same day in the same way, prompting NSW police to issue a public warning on social media.

The Mini Cooper was stolen from the driveway of the Jerrabomberra home just after 7.15am, with the owner returning after five minutes to find it gone.

Acting station sergeant Jayde Evans, from police traffic operations, had some simple advice for people who leave their cars to warm up on frosty Canberra mornings: don't do it.

"Like many instances of theft, car theft is often a crime of opportunity," sergeant Evans said.

"Even a car left unattended for a minute or two, whether it is to warm up in a garage or to defrost in a driveway, can be a target for thieves.

"While it is important to defrost a vehicle windows and mirrors before heading off, you should never leave a running vehicle unattended."

Police tips on how to keep windscreen frost at bay

In each of the Monday thefts, the car thieves' modus operandi was identical: wait for the home owner to come out and start the car, leave the engine running and heater on, then steal it.

The family Volkswagen was reported as yet another stolen car in Canberra, one of 273 taken in the first three months of this year. Last year, 1074 motor vehicles were reported stolen to police.

If the car is been stolen by joyriders, it may be recovered undamaged. If it has been stolen to be used to commit another offence, such as a ram raid or burglary, the odds dramatically increase that it will be taken to a remote area and incinerated to remove any evidence.

Compared with the rest of Australia, measured by theft rate per 1000 registered vehicles, the ACT is second only to the Northern Territory.

Those who have their car stolen while the engine running also get hit with an unexpected double whammy; insurance usually won't be paid out because in the view of the insurer, the vehicle was left unsecured and unattended.

"We had no idea of the extent of the financial cost and inconvenience this has had on us," one owner said.

"The spare electronic key to our other car was on the keyring of the stolen car so that cost $1300 to replace, we had two child seats in the back which are $500 each and we've had to hire a car while we wait to see if our car is found," she said.

"Our five-year-old son had left his school bag and his favourite jacket in the car. He cried all the way to school."

She said that losing the insurance claim was another possibility they hadn't considered.

"If we don't get paid out, we will be out of pocket by as much as $10,000," she said.

From a police perspective, if you drive a vehicle "without a clear view" such as with frost obscuring your windscreen, this could incur a $200 fine. But conversely if you leave a vehicle with the engine running and unattended, the potential penalty is a $200 fine.