Barbara Diane, if I may, I'd like to add another perspective. Not disagreeing with Angie at all -- just elaborating a bit based on my locale.
I used to be an end of season bargain shopper and it did not work for me. I still do occasionally find a lucky end of season sale to stock up on essentials or basics (like socks!!) but on the whole, since joining YLF, I FAR prefer to shop early in the season.
Having said that, living in an extreme climate area, I find that retailers tend to stagger their offerings a bit more than they might in the more temperate Pacific Northwest, and you won't necessarily find the best stuff for my climate in August or early September (apart from the NAS).
It all depends what you are shopping for.
For toppers -- yes. Start looking seriously at the end of August and into September/ early October.
For footwear? Begin looking in September.
For heavier or cashmere/ wool sweaters? Begin to look around the end of September and into October.
Ditto for winter coats. If you are lucky you might begin to find these items in mid-September in the big department stores, but the full range won't really show up until early October as a rule.
If you want holiday bling, shop in November.
If you want a sale on knitwear, wait until after Christmas and cross your fingers that you will find something to refresh your capsule.