They are like humans without water, they will die. Don t forget these other winter hazards. The warm engines of cars attract cats. Salt and chemicals used to melt snow and ice can burn the pads of pets feet. And antifreeze tastes sweet but is poison to pets.
Birds are desperate for food in the weather when the ground and trees are frozen.
Spreading bread crumbs, corn bread and sunflower seeds across the yard will help them survive. Stock up on birdseed. If you don t have feeders to fill, clean a place in the snow and put seed out. Make sure they have some water. Boy Scout Road.