I have family obligations today that kept me out of the woods, need my pork & sauerkraut for good luck.
My opinion is that, deer like humans and other animals, burn more calories when it's bitter cold. Since more calories are burned staying warm, then it reasons that more calories need to be consumed. Hence deer need to eat more, which in turn causes them to move more at times when they normally wouldn't.
Also, with several inches of snow on the ground, I have to think it takes more time for the deer to find and consume certain foods, such as acorns. And then, since it takes more time and energy, it requires more calories, which all ties in with the need to spend more time eating.
Of course, the deer will still need rest and will bed down. Maybe, since their rest time is limited, they will rest more soundly, leaving them more vulnerable to predators like us?
I could be wrong on all this, but I'd bet that the deer will spend less time bedded down during times of severe winter temps than at any other time of the year. And when they do bed down, it'll be fairly close to their food source....
I kill because I'm hunting, but killing is not the reason I go hunting.