Many car owners know it’s not a good idea to leave their car running and unattended.

But they still do it, especially when it’s cold outside.

Known as puffing, this practice attracts car thieves. Leaving a car idled without anyone inside is illegal in Colorado and happens more often during winter months. Law enforcement agencies and experts say owners do this because they want to warm up their cars while they run back inside to get a cup of coffee or their briefcase.

Thieves see this as an ideal opportunity.

“Someone can steal your vehicle and the vehicles can be used in other crimes,” Colorado Springs police spokesman Lt. James Sokolik. “That vehicle may or may not be recovered in the condition that you can use it again.”

Colorado cops target puffers: Vehicle idling crackdown starts soon

In January, 24 puffing cars were stolen in Colorado Springs, police said.

Police also reported that 21% of the vehicles stolen in the city last year were left with the keys inside. This number comes from vehicles that police identified how they were stolen.

The highest risk for having a vehicle stolen is leaving it unlocked and unattended with the keys left inside, according to Colorado Auto Theft Prevention Authority, which reported that 15% of stolen cars were connected to other crimes.

So named for the puff of exhaust from the vehicle, the practice comes with a $60 fine on first offense, though a Colorado law states that vehicles with remote-starters are exempted from being ticketed if they are found running unattended.

A few days of extreme cold this week have put this issue into the spotlight once again. Temps dropped to single digits across the Pikes Peak region, presumably prompting some owners to leave their car unattended while it warms up.

Pueblo police reported Wednesday morning its first puffer theft.

“We understand that it’s extremely cold this morning and that you may want to warm up your car, but please don’t leave your vehicle running and unattended,” Pueblo police posted to Twitter. “Thank you, and stay warm!”