1.Keep your cat inside. Outdoors, felines can freeze, become lost or be stolen, injured or killed. Cats who are allowed to stray are exposed to infectious diseases, including rabies, from other cats, dogs and wildlife.
2.During the winter, outdoor cats sometimes sleep under the hoods of cars. When the motor is started, the cat can be injured or killed by the fan belt. If there are outdoor cats in your area, bang loudly on the car hood before starting the engine to give the cat a chance to escape.
3.Never let your dog off the leash on snow or ice, especially during a snowstorm, dogs can easily become lost. Make sure your dog always wears ID tags.
4.Thoroughly wipe off your dog’s legs and stomach when he comes in out of the sleet, snow or ice. He can ingest salt, antifreeze or other potentially dangerous chemicals while licking his paws, and his paw pads may also bleed from snow or encrusted ice.
5.Never shave your dog down to the skin in winter, as a longer coat will provide more warmth. When you bathe your dog in the colder months, be sure to completely dry him before taking him out for a walk. Own a short-haired breed? Consider getting him a coat or sweater with a high collar or turtleneck with coverage from the base of the tail to the belly. For many dogs, this is regulation winter wear.
6.Never leave your dog or cat alone in a car during cold weather. A car can act as a refrigerator in the winter, holding in the cold and causing the animal to freeze to death.
7.If your dog is sensitive to the cold due to age, illness or breed type, take him outdoors only to relieve himself.
8.Does your dog spend a lot of time engaged in outdoor activities? Increase his supply of food, particularly protein, to keep him, and his fur, in tip-top shape.
9.Like coolant, antifreeze is a lethal poison for dogs and cats. Be sure to thoroughly clean up any spills from your vehicle, and consider using products that contain propylene glycol rather than ethylene glycol.
10.Make sure your companion animal has a warm place to sleep, off the floor and away from all drafts. A cozy dog or cat bed with a warm blanket or pillow is perfect.
Taken from http://www.aspca.org/pet-care/cold-weather-tips