The temperature where I am is about 65 degrees, which is odd for December. It's hard to get into the Christmas spirit amidst global warming, but there's always movies to put you in the mood. However, if you're looking for something without the sugary sweetness of Christmas family films, you might try movies that "revolve around cold, and snow, and hypothermia and madness." Five of them are detailed at Unreality. Pictured here is the “snow-nazi-zombie” movie Dead Snow. Link
Real zombies lack the ability to produce body heat. They freeze when the water in their bodies freezes.
However, the original zombies, the ones in Haiti that are kidnapped and poisoned (and brain-damaged in a very specific way) are still eating and living. The disease victims in the Walking Dead are called zombies, and I guess they fit that definition -- are an interesting case. They do need to eat and if they do not eat, they fall into a torpor to conserve energy.
Recall -- in the first season, our group of survivors were guests of the CDC in Atlanta which was still being kept online by a PTSD affected scientist. His MRI scans showed that the Walkers were still indeed alive, including an obvious and measurable brain wave pattern, albeit restricted to the lower level systems. As for the heads of the Walkers still being dangerous after decapitation, we don't know how long they live because the show never lets one live more than a few moments before our heroes kill it. I suspect that the head would die after a few minutes, much like a decapitated snake, who has neural systems similar to the systems that are still functioning in the walkers. Maybe this might help you suspend your disbelief when you consider the Nazi snow-zombies? Oh....another thought....the Walkers, even though it's obvious their biological functions are still able to intake nutrients and pump enough blood and maintain respiration well enough to hang on it is also obvious that they are slowly decomposing.
They are steadily decomposing due to their inefficient circulation. Decomposition does produce heat - you know, like when it's freezing out, but your compost heap is still well above freezing?
The zombies, like warp drive, space travel and end-of-the-world scenarios (and etc.), when used constructively, make very effective plot devices -- and a fun way to explore, in mock-earnestness - what-if scenarios with fellow members of the online commentariat.
Based on memoirs, interviews and comments made by aerospace engineers & officials, designers, military folk, academics and others, Science Fiction has been a real source of inspiration and the reason a lot of these smart people chose science as a profession.
(BTW -- I really enjoy Neatorama and the effort ya'll spend on it. Your blog's new redesign rocks too. I am happy that the comment volume is increasing - my fellow readers, and the moderators seem like a mellow, intelligent group of peeps.)