right after the new year’s models arrive en masse. It seems like a car-commercial cliche, but they apparently really do need to make room for the new models, and that’s typically when you see the really big incentives and stuff. That’s usually November-January. You’ll see the best deals on cars that weren’t moving the previous year. Check out the manufacturer’s sites, and you’ll often see lists of incentives.
Also, winter is the best time to buy a convertible.