I just read a post that suggested to use the time now to plan for starting on Jan 1st. That is horrible advice!!

Most properties I have ever bought, were purchased during fall and early winter. Back in 2010 banks wanted to get rid of their REO before the end of the year, later it was short sales, today it's just regular sellers that are seeing the leaves turn, we may get the first night frost this weekend, showings are slowing down more and more every week - seller anxietly is growing.

If you look at the chart you can see an over 10% swing betweeen highs and lows. That is partially amplified due to the fact that more of the nicer homes get listed and spring, so that skews the data to some extend. But I would say for the same house, you can expect a 5% lower price compared to last spring and more compared to next spring. 

But don't take my word for it, here is a chart that shows a very reliable pattern.
How is your market?