It's something anyone who lives is a cold climate has probablydone–gone outside to turn the car on to defrost and warm up, andthen gone back into the house or apartment.

With the cold weather gripping much of the nation, thousands ofdrivers are starting their cars and leaving them idling for a fewminutes while they warm up on these frigid mornings, but police sayit's a bad idea because it creates a crime of opportunity forthieves. Just this month, several dozen cars in six states werestolen as their drivers left them idling in driveways or on thestreet. Eleven cars were stole in a single morning in Indianapolisearlier this week.

This type of crime usually spikes in the winter months. In St.Louis, 16% more cars were stolen in January 2014 than the previousyears. Officials are worried because the crimes usually occur inthe mornings when students are waiting for school buses and thethieves will take off at a high rate of speed, endangering anyonein their path. In some areas, gangs of thieves are watching driversstart their cars and then swoop in to steal several cars in asingle neighborhood.

A check with several national insurers shows that cars stolenwhile idling will still be covered by insurers for theft, althoughauthorities recommend against leaving a car running without anyonein it, because the driver may be violating some local ordinancesthat could result in a ticket or fine, or in some cities evenimprisonment. Most fines run between $100 to $500, and some statesstart at $500 and go as high as $2,500.

Several states limit acceptable idling times to anywhere fromthree to 15 minutes in a given hour. In Minneapolis, drivers mayleave their cars idling if they need to “operate defrosters,heaters or air conditioners to prevent a safety or healthemergency.” If the outside temperature falls below zero degrees orhigher than 90 degrees, cars may idle for up to 15 minutes withouta ticket.

According to the U.S. Department of Energy, most of today's carsdo not require more than 30 seconds to warm up. If a car will besitting for longer than 10 seconds, it will require less gas torestart the car than to leave it idling for several minutes. Anidling car can burn as much as a half-gallon of gas in an hour, soturning the car off is more fuel efficient and causes less airpollution.

Police in St. Louis say that if drivers must leave their carsidling, they should have two sets of keys so the car can be lockedwhile running and the extra set can be used to unlock the door whenthe driver leaves. Remote car starters also allow drivers to starttheir cars while locked and require the key be in the ignitionbefore it can even be put into drive, making it harder for thievesto steal.