Drivers who leave their car running to defrost while they stay warm in the house are breaking the law, police say.
The reminder that it is illegal for motorists to leave their car unattended with the engine running comes as Britain faces some of the coldest weather of the year.
With the temperature dropping below zero, many motorists are waking up to find their car iced over in the mornings. Some turn the engine on to get the heaters blowing and melt the ice while they stay inside the house getting ready.
However, a spokesman for Staffordshire Police told The Birmingham Mail: "Anyone who needs to defrost their vehicle must ensure they stay with it and don't leave it unattended with the keys inside.
"Drivers should always be in control of their vehicle when the engine is running, even when they're loading or unloading shopping or baggage.
"Leaving the engine running to warm up during the winter months not only risks having the vehicle stolen, it's against the law.
"Don't make it easy for opportunist thieves because they don't even have to go to the trouble of breaking into your vehicle if you have left it running for them.
"Insurance companies may not pay out if a vehicle is stolen in this way."
On Tuesday morning, the Central Motorway Police Group tweeted that six cars had been stolen in a 30-minute period because cars were left unattended to defrost.