Dog natural adaptations to the cold:
Countercurrent circulation is found in all dog breeds and helps to keep their paws from freezing
In addition, the fats in dog paw pads remain liquid and flexible at much colder temperatures than fats in the human body. Our fingers and toes are like sticks of butter in cold temperatures while a dog's paws are more like canola oil in the cold - still liquid and much more flexible than our frozen butter fingers in the cold!
Double fur coat
Double coated breeds have a downy undercoat layer that is the dog equivalent of a puffy down jacket to keep them warm On top of that they sport long, coarse guard hairs (like a gore tex jacket) that helps shed snow or moisture. These breeds are well suited to snow and cold without any additional jackets or warm layers. However, many other breeds who only have a single coat or very thin coat may need to wear a warmer jacket when out in cold, snowy conditions to help them regulate their temperature.
If any dog (regardless of their fur coat) gets snow packed through their fur and right next to their skin (think sleet, wind driven snow, anc other challenging weather conditions) they are at risk of hypothermia and it is important to get them calories to help them regulate their temperature and get them warm and dry as soon as you can.
Winter hazards
Ice melt on sidewalks or roads. Many can be toxic to dogs so clean their paws off if you suspect they may have walked through some. If you plan on using any snow melt products look for ones that are dog friendly.
Antifreeze This product tastes sweet and can be appealing to dogs, but it is also incredibly toxic. If you suspect your dog drank antifreeze contact your veterinarian right away.
Overall health
Exercise. Many humans struggle to get out and exercise outdoors in winter when days are shorter and colder and wetter. However, dogs (and humans) benefit greatly from maintaining a regular exercise program in the winter months. It is good for all of us mentally and physically to get out and play every day.
Hydration. Just like humans, dogs may not be as interested in drinking water in the cold weather. Make sure your dog is staying hydrated in winter just as much as in summer. Consider baiting water with a spoonful canned tuna or soaked kibble if your dog doesn't like to drink water in the winter.
Supplements. If your dog has dandruff due to dry weather or because of forced air heating, consider adding a fish oil supplement to help their skin and coat stay healthy.
Weight. Make sure your dog is maintaining a healthy weight. It is easy for dogs to add weight in winter if they are spending more time indoors and less time running around outside. Here is a helpful chart for determining a dog's weight. Where does your dog register on the chart? Don't just look at your dog. Use the palm of your hands (not your fingertips) to feel for their ribs, their vertebrae, their waist, etc. Your dog will enjoy their outings with you more and be less at risk for athletic injuries if they maintain a healthy weight.