Here's a winter habit you'd do well to break: Don't start your car and leave it to warm up outside your home.
Car thieves just love that.
As your car "puffs" out exhaust, thieves are on the lookout for the telltale smoke signals that announce an unattended vehicle.
Gregory Kehrl was warming up his Mercedes in front of his house when he went inside to get his wife.
And in that moment, someone drove off in it.
"I went running down the street and was like 'Hey! That's my car!''' he told INSIDE EDITION.
Adding insult to injury, the car thieves came back that night, armed with Kehrl's keys, and stole his other Mercedes.
Octavia Patton left her car running, with her son, Eli, strapped into his car seat. She had gone into her mother's house to retrieve a bag when someone drove off with her vehicle. And her son.
"The thought that went through my mind was that I might not see my son again," she told IE.
The car was abandoned a few blocks away with Eli still inside.
INSIDE EDITION rode along with police in the Colorado suburb of Aurora, where hundreds of "puffing" cars are stolen each year.
LT. Stephen Redfern says "what they'll do is exactly what we're doing-looking for the exhaust."
It's illegal to leave an unattended, running car outside in this town, but Redfern often just gives owners a warning.
"In the future, don't leave it running, OK?" he tells one man.
"OK, thanks," said the grateful car owner.