Why do my tires always go flat in the winter?
There are several reasons why your car's tires may go flat when it is cold:

1. Leaking Tires: If there is a small hole or leak in one of your tire, air will escape and cause the pressure to drop, which can lead to a blowout. You should have your tires rotated regularly (every 7-8 weeks) so that any worn out parts can be replaced before they become a problem. Replacing even a single punctured tire could save you from a very expensive repair bill!
2. Dehydration: When temperatures fall, water vapor in the atmosphere condenses on exposed surfaces such as windows, mirrors, windshields, etc. This condensation forms tiny droplets that gradually grow into larger drops until they reach the ground where they freeze, forming a layer of ice. The same thing happens with water molecules inside your tires - but instead of freezing at the bottom, they continue migrating upwards towards the tread surface. Over time this process causes gradual softening and corrosion of the rubber compounds that make up the tire carcass. 

To prevent this type of damage, keep your vehicle properly lubricated by regularly checking its oil level and using synthetic motor oils designed for low temperature performance. In addition, rotate your tires every month or two to ensure proper wear distribution and uniform inflation pressures. Finally, defrosters can also help melt away excess moisture preventing future issues.