Always does. Sept-Dec is ALWAYS the weakest time of year. In NYC the jump will happen before the spring, as Wall St. bonuses are projected to rise 15-25% above last year's record levels. In 2005 those people wiped out all existing inventory, leading to a massive spike in prices thereafter.
"The growing inventory in Northern Virginia appears to have finally reached a plateau. Historically August has been the peak month for the inventory of available homes. Inventory of available homes is at a five year high."
Well, here in "mid-America" people have their kids in school and so they can't think about moving until May/June, so, allowing a couple of months to shop for a home, then close, that puts you about April to start buying. Plus, houses don't LOOK as good with 2 feet of snow in front of them, so that's a drawback to winter sales.