It looks as though the annual Steam Winter Sale will begin on December 22.
This news is according to a promotional holiday offer page on Paypal's website, where you're invited to buy a Steam Digital Wallet Code before the sale starts on December 22.
Valve hasn't had a great year of keeping its sale dates secret, and PayPal also leaked Steam's Autumn Sale dates last year.
The December 22 date isn't confirmed yet, but it seems like a good bet. IGN will update you when we know more.
If you can't wait for those wintery PC deals, check out IGN's Daily Deals in the meantime.