The USDA Plant Hardiness Zone Map. Considered the standard measure of plant hardiness, the USDA Zone Map is generally is based on the average annual minimum winter temperature, divided into 10-degree F zones.
August may be a great time to buy certain kinds of cars, and the first couple of days of the month could be an opportune time to seal the deal. Then again, depending on the buyer and car model in question, those times might not be ideal to get the best price.
The best time to buy a new car is when the dealer is willing to negotiate and you've got more leverage. But you have to be a good negotiator. Don't be afraid to hit the road without a new car if the salesperson isn't giving you the price you want. There are other dealers in town, and be sure to remind him of that fact.