When a vehicle sits for a long period of time, the tires can experience flatspotting. Flatspotting is the term used when a tire gets a flat spot in the area touching the ground.
When a tire stops moving, it cools and keeps a memory of where it last touched the ground. In most cases, flatspotting is a temporary condition that is remedied by simply driving the vehicle. As the vehicle moves, the tire warms up and rounds out, eliminating the flat spot. In more severe cases, the tire is permanently damaged. Cold weather and tire composition play significant roles in the severity of the damage.