MILWAUKEE, Wis. (CBS58) -- So far in 2018, 45 cars have been stolen in the city of Milwaukee, according to police. Since Dec. 28, 105 cars have been taken. 

During the cold months, thieves are watching for unattended cars. People are leaving the key in the ignition.

"Historically we have seen a spike in stolen cars during these months because individuals decide that they're going to warm up their car leave the keys in the car running outside and as a result the cars are stolen we I don't want to see that," said Milwaukee Mayor Tom Barrett. 

Leaving the key in the ignition is a violation of city ordinance. Police can give you a $22 ticket. 

"You're going to have use real common sense here to make sure that if you're doing this that your car is in a situation where it's not going to be stolen," Barrett said.