A warm car is more inviting when you get back behind the wheel, but it's also illegal if your doors aren't locked.
"I pretty much go turn it on, run back inside and come back out when it's warm because it's just freezing," said Jennie Vasquez, who lives in Reading.
Vasquez blasts the heat after she turns her car on, then she darts inside as it warms up.
"I always lock it and then I come back out, and I always bring my remote," Vasquez said.
But many other drivers simply leave the keys in the ignition with the doors unlocked while the car is still running.
"We see people leave their car on and they go back inside and have a cup of coffee, or they'll sit down for a little bit for the car to warm up and then they'll go right back out," said David Martinez, who didn't know it was illegal to leave a car running and unattended in Pennsylvania.
Thieves are on the prowl looking for vehicles that are easy to steal, and leaving it running to warm up can end up leaving you out in the cold.
"Somebody walking by sees the opportunity to steal the vehicle and does so in that moment, so it's as quick as a second," said Sgt. Jacquelyn Flanagan, Reading Police Department.
According to Reading police, a minivan was stolen on Jan. 8 in the 1000 block of Elm Street after it was left unattended.
During this bitter blast, patrol officers have been out looking for vehicles left running with no one behind the wheel because it's a vehicle code violation and against state law.
"We issue a ticket or a warning to let owners know that this is a crime, and let them know ultimately they can become a victim," Flanagan said.
Police recommended using an automatic start button to help your car warm up, or simply stay inside the car.
Anyone who violates the law could be issued a summary offense, which could cost $88.