Rock salt, used to melt ice on sidewalks, may irritate footpads. Be sure to rinse and dry your dog's feet after a walk. Provide plenty of fresh water. Your dog is just as likely to get dehydrated in the winter as in the summer. Snow is not a satisfactory substitute for water.
Frostbite is a winter hazard.
To prevent frostbite on ears, tail, and feet, don't leave your dog outdoors for too long. Be very careful of supplemental heat sources. Fireplaces and portable heaters can severely burn your dog. Make sure all fireplaces have screens and keep portable heaters out of reach. Like people, dogs seem to be more susceptible to illnesses in the winter.