Using common sense is a biggie regarding dogs and the cold. My biggest time to hunt is the Split season in western NY(12/27 -01/11). I exclusively hunt the Niagara river. The water is barely over the freezing mark and the current to about 6mph. When my dog starts to really shiver , I turn on the heaters in the blind and in a matter of minutes he's all dry and ready to go. Those neoprene vests are the ticket. they keep is torso and vital organs worm and dry. If I get a day that is really cold then I periodiaclly take him for a walk,bring him to the truck for a warm up , or run him to get the circulation going.
Last year we had a day that was terrible. 30-35 mph winds, snow and about 5 degrees with the wind chill. Canvasbacks,Redheads,Bluebills and Goldeneyes were just pouring into our set. The dog worked his butt off, but when he got too cold I left the blind and made sure I warmed him up. My buddies say I might baby the dog too much. All I tell them is that he's not a tool , he's a member of my family and I'm not going to jeopardize his health just for a few ducks.