Westminster, Colorado, police warned drivers Monday that warming up your car by leaving it running unattended — “puffing” — is illegal under state law and makes vehicles “easy targets” for thieves.

The reminder is part of a broader push by Colorado law enforcement to cut down on cold-weather auto thefts tied to idling cars left unattended in driveways and parking lots. Colorado’s “unattended motor vehicle” statute requires drivers in charge of an unlocked vehicle to stop the engine and remove the key before leaving it, with a limited exception for remote starter systems if the driver takes security measures. (RELATED: Motor Vehicle Thefts Skyrocket To Highest Level In Decades, FBI Data Shows)

“Puffing is also ILLEGAL in Colorado (immobilizing remote start systems excluded) and may result in fines. Just don’t do it,” the Westminster Police Department wrote in a Feb. 14 public safety post.

The mornings have been a bit chilly! Remember, puffing (leaving your car running unattended) is ILLEGAL in Colorado. These are easy targets for thieves! Learn about more ways to prevent auto theft at https://t.co/BQxFwGe0XB.

*Immobilizing remote start systems are excluded pic.twitter.com/7KCTU4HLki

— Westminster Police (@WestminsterPD) December 29, 2025

Colorado State Patrol has warned that “cold Colorado mornings always lead to an increase in puffer vehicles,” noting that the practice can result in fines and can leave drivers “out in the cold” when a thief drives off.

Other agencies have paired the message with stepped-up enforcement. During a past statewide “Puffer Week” campaign, the Douglas County Sheriff’s Office said deputies would increase warnings and “likely citations” for cars left running unattended, adding that “the first offense costs $60.”

Colorado’s LockDownYourCar.org — an auto-theft prevention effort — tells drivers it’s illegal to leave a vehicle running unattended unless it has a remote starter system and the keyless fob is far enough away that the car can’t be moved.