There are very few industries that know how to frequently handle turnarounds with inventory like car dealerships. It is not an every day routine decision to wake up and purchase a car, and car salesman know that. Which is why when dealerships have a large variety of wholesale cars there is typically a formula behind it.
The general public tends to purchase their cars during the 2nd& 3rd quarter of every year. This is peak season for car dealerships, and typically when people are receiving their income tax checks. It is also much wiser for consumers to purchase cars during the spring and summer season because they avoid what is almost inevitable.
Car dealerships hold special event/discount sales during the late 3rd and 4th quarters of each year for a variety of reasons. Weather damage from hail and/or snow plays a major part in inventory. If a car has visible exterior damage, salesman are prepared to know that they have to provide some type of markdown for a consumer willing to purchase the vehicle as is. Additionally, holidays such as Thanksgiving, Black Friday, Christmas, and New Years Eve/New Years Day, are opportunities for dealerships. It gives them the room to push out last years inventory, while not letting cars sit and lose value (which in the end results in them potentially losing profit). This also benefits the consumer to save a little bit of money on their end, which becomes a win-win for everyone.