Generally speaking, you can't. From what I've seen, furs (and by furs, I mean furs sold at a fur salon or fur department in a department store, not designer boutiques) only go on sale at the end of the winter season. They are a little less expensive in the summer, but not drastically (most people buy furs then because often a fur coat is custom-made to your measurements, or there is at most a very minimal stock). You could comb through high-end vintage boutiques and consignment shops, or if you're really courageous and knowledgeable about furs, you could try online, those are your best bets for finding deals. Typically, someone who is selling a high-end fur knows what it's worth and isn't about to give someone a deal on it.
Prices vary heavily depending on the type of fur though. What would you be looking to buy?