Blame it on the weather.
Up North, thieves are making off with cars left idling to warm up in the dead of winter.
Down South, they're swiping cars left running with the keys in the ignition in the sweltering summer as the owners run into a store to grab a cold drink.
And that leaves drivers on both sides of the Mason-Dixon Line sweating or shivering as they wait for the cops to arrive.
More than 700,000 vehicles are stolen in the United States each year, and up to half the thefts can be blamed on driver error -- including leaving doors unlocked and leaving keys in the car, according to the National Highway Traffic Safety Administration (NHTSA). Only about half are recovered.
St. Petersburg, Fla., Police Department spokesman Bill Proffitt saw it firsthand in a city where a stunning 83 percent of car thefts last year could be blamed on people leaving their keys in the car.
The department recently formed a new unit aimed at preventing car theft. When the unit pulled up to a convenience store to make an auto theft awareness video, they found a motorist had left his BMW idling in the parking lot and gone inside. Teenagers jumped in the car and sped away.
The driver told police he'd been keeping an eye on the car from inside the store.
"How's that working for you, buddy?" Proffitt asked facetiously.
Man up, Minnesota
It's not much better in Minneapolis, where more than 300 vehicles were stolen between Nov. 1 and Jan. 17, and most were swiped from drivers who left their cars idling outside in the bitter cold.
"We're Minnesotans. Dress warm and sit in your car for five minutes," says police spokesman John Elder.
By leaving your car idling in the driveway with the key in the ignition, "you might as well just call yourself a victim," Elder says.
If it's mind-numbingly cold outside and you must warm up your vehicle, Elder suggests using a remote starter, which will keep you within the bounds of the law.
Another option works if you have two keys. You can keep one in the ignition to leave the engine running and lock your car with the second key, then head inside while the car warms up.
While that may deter car thieves, "it doesn't meet the spirit of the law," Elder says.
Tickets for cars left idling
To reduce the theft of vehicles that are left running, and to reduce air pollution, both St. Petersburg and Minneapolis are among a growing number of jurisdictions that either prohibit or limit the amount of time you can leave your vehicle idling.
Ignore the law, and you could face fines. In St. Petersburg, the city now will slap you with a $116 fine as the number of stolen vehicles soared to 1,124 last year, up almost 30 percent from 2012.
In Minneapolis, you can't leave your car running on public property, including city streets. On private property you can let your vehicle idle for three minutes most of the year. When the temperature plunges below zero, you can leave it running for 15 minutes.
Break the law, and you could have to cough up $200.
Confronted by a similar wave of thefts - 36 thefts of unattended, idling cars - the city of Ogden, Utah, this week began issuing $40 citations to drivers who leave an unattended car idling for any time at all.
In other places, the law applies to the entire state. If you leave your running vehicle unattended in Ohio, you could be charged with a misdemeanor and fined $150. In New Jersey, leaving your vehicle idling for more than three minutes could cost you $250.
Are you covered - even if you left the car running?
The tickets for leaving the car running generally won't appear on your motor vehicle record and thereby affect your car insurance rates. But by leaving your keys in the car, you may run the risk of having your insurance claim denied.
CarInsurance.com consumer analyst Penny Gusner says some auto insurance policies may contain language that allows insurers to deny a claim if you haven't taken reasonable care to safeguard your vehicle, such as leaving the keys in your car.
"I believe that most policies will cover you. However, it's always best to read through all exclusions of coverage on a policy," Gusner says. "In this case, it would be exclusions to your comprehensive coverage benefits."
You also will be stung if you don't have full insurance coverage on your car.
Owners of older vehicles might have dropped their comprehensive insurance, which covers thefts, in order to save a few bucks. (The list of most-stolen vehicles by state shows very few newer models.) If you're among them, you'll be shelling out the cash to replace your car.