I have been following the cull cow market for twenty years and I have analyzed historical data since before I was born. Of all agricultural markets, this market is more consistent more predictable than any others I have analyzed. I have looked at cull cow price data from Billings, MT to Amarillo, TX, from Salina, UT to Lexington, KY. The seasonal patterns are nearly identical.

Cull cow prices increase from January through about April, and then maintain or increase slightly in value through August and then prices decline rapidly into October. The prices remain seasonally low through November and then, here is the big unknown, sometimes they stay low in December and sometimes they increase in December. You can take that to the bank. The most reliable part of this seasonal pattern has been the decrease from August to November. In the last 20 years, there has only been one year when prices were higher in November than they were in August; 2003 the year the border was closed to Canada and steer prices increased 50% in a couple of months time.
The typical decline from August into November is about 15% in most markets. In dollar values, that would be a decrease of almost $7 per cwt. if cows were at $45 in August to about $38 in November.
To read the entire article, link to Feuz Cattle and Beef Market Analysis.