Autumn precedes it. Granted, the sale isn't given the same attention at Valve's end as its Summer and Winter cousins, however the scope of the sale is the same -- it's just shorter in length (one week versus the Summer Sale's one-and-a-half weeks and the Winter Sale's two weeks).
Last year's autumn sale had the same prices as last year's winter sale, as well. So it's like an exteneded winter sale with a long intermission. :O