From my experiences, if it's a storm, snow, mixed with wind, they lay up for a while. But at some point they have to get up. Now just snow without wind man I've seen them go flat stupid. I shot the biggest buck I've ever seen on the hoof the morning after a snow storm. It was flat calm, cold and about 2-3 inches still on the ground. Regardless of what it's doing, you can't kill'em sitting on the couch.....