West Midlands Police have issued a ‘frosty morning warning’ after 13 vehicles were stolen within 36 hours.
Each theft occurred when the victims left their cars unattended with the keys in the ignition while the vehicle warmed up.
Chief Superintendent Jon Hesketh, from West Midlands Police, said: "People think it is fine to leave their cars unattended for just a moment, but a moment is all it takes for the car to be stolen.
“Opportunist thieves are aware cars will be left unlocked to warm up - and they will take your car if you give them the chance."
Car insurance companies can refuse claims where claimants have left cars unlocked, unattended or with keys left unattended in the ignition.
Police have also urged motorists not to take any safety risks by failing to clear windscreens properly before driving.
Drivers can also get vehicle crime prevention advice by visiting the Safer Motors website at www.west-midlands.police.uk/safermotors.
Anyone who may have witnessed any suspicious activity is asked to report it to their local police station on 0345 113 5000.