Does My Dog Need a Winter Coat? How to Tell, by Size, Fur and Age

Dogs that usually benefit from a coat

Cornell says: "Especially for smaller breeds, older dogs or those with a thin coat, a jacket or sweater will help keep them warm in the winter." Its general guidelines explain why each group struggles:

• Small dogs. "Small-sized dogs have a harder time staying warm compared to larger breeds."
• Short-haired and thin-coated dogs. "Short and thinly-coated breeds will not tolerate the cold as well as thick, double-coats, such as Siberian Huskies and Malamutes." The ASPCA's advice for a short-haired dog is to "consider getting them a coat or sweater".
• Puppies. "Puppies cannot properly regulate their body temperature and have very little body fat, making them more susceptible to the cold."
• Old, underweight or unwell dogs. "Older animals, underweight animals or those with other medical conditions may have difficulty staying warm or regulating their body temperature in the cold."
• Dogs not used to the cold. Cornell notes that dogs "not already conditioned for cold temperatures (i.e., coming from a warmer climate or exposed to a sudden cold snap) will be less prepared to handle the arrival of cold weather."

Breed gives a first hint. A Texas A&M veterinarian put it this way: "Dog breeds such as Siberian Huskies or Saint Bernard's are bred to handle cold weather, while others like Chihuahuas or Greyhounds are not." The same article says that pets with health conditions can go outside for short, supervised periods in cold months, but "these pets may need sweaters or boots to keep them comfortable."

Dogs that usually need a coat less

Dogs bred for cold weather, with a thick double coat, tolerate low temperatures better than the groups above. That does not make any dog immune. In Cornell's words, "every dog (and human) is susceptible to the cold," so the advice is to watch your dog's behavior outside and "adjust their exposure time accordingly."

For a long-haired dog, a longer coat provides more warmth, so avoid shaving it down. The ASPCA's advice: "Never shave your dog down to the skin in winter. A longer coat will provide more warmth."

How cold is too cold?

There is no single number that fits every dog. A Texas A&M veterinarian explained that the answer depends "on many different factors, from fur thickness and length to body mass," which "makes it hard to determine an exact temperature that could be dangerous to your pet's health."

The same veterinarian gave one reference point, about leaving pets outside: "it is clinically accepted that indoor pets that are not acclimated to cold weather should not be left outside when the average daily temperature is below 45 degrees Fahrenheit." That figure comes from a 2009 article and is a guide for time spent outdoors, not a rule for when to put a coat on.

The simplest test comes from the ASPCA: "if it's too cold for you, it's probably too cold for your pet."

Signs your dog is cold

Your dog's behavior is the best guide, because tolerance varies from dog to dog. Cornell says to move your dog into a warm and dry area if you notice any of these signs:

• Shivering
• Whining or barking
• Tail tucking or hunched posture
• Lifting paws off the ground
• Reluctance to walk
• Suddenly anxious behavior

On shivering, the Texas A&M veterinarian said: "Pet owners should watch for shivering, because it is a mechanism used to compensate for being cold. However, constant shivering may mean that the pet is uncomfortably cold."

If your dog shows these signs, move it somewhere warm and dry. A coat may help, but if the signs appear even in a coat, shorten the walk or stay inside, and ask your vet if it keeps happening.

What a good winter coat covers

• Coverage. For short-haired dogs, the ASPCA suggests "a coat or sweater with a high collar or turtleneck with coverage from the base of the tail to the belly."
• Belly and chest in snow. Cornell notes that "some jackets that cover most of the body will help deter snowball accumulation on the belly and chest, especially for smaller breed dogs whose bodies are closer to the ground."
• Fit. In Texas A&M's How Cold is Too Cold, a veterinarian described both ways it can go wrong: "The sweater should not be large enough to hang loosely or produce gaps that can prevent the animal from keeping warm. On the other hand, you do not want a sweater that is too tight and can cause circulation problems or irritation to the animal's skin."
• Supervision. The same Texas A&M article on pet clothing: "never leave the animal unattended," because clothing "can get caught on numerous things outside and that can injure the animal."

To get the size right, see how to measure your dog for a sweater or coat: chest, neck and back length.

A coat does not replace common sense

• Limit time outside. Cornell: "When the temperatures are too cold, dogs should not be left outside for long periods of time." Prolonged exposure "can lead to frostbite or life-threatening hypothermia," and "ears, paws and tail tips are most commonly affected." Most coats leave the ears, paws and tail tip uncovered.
• Protect the paws. Cornell suggests you "train your dog to wear well-fitting booties to protect their paws," and to "wipe or wash paws to remove salt, de-icers or snowballs after returning inside."
• Never leave your dog alone in a cold car. The ASPCA warns that "cars can act as refrigerators that hold in the cold."
• When to call the vet. Cornell: "If you are concerned your dog is experiencing frostbite or hypothermia, they should be seen by a veterinarian immediately."

Does a dog need more food in winter?

It depends on how your dog spends the winter. Cornell says that dogs who "choose to spend lots of time outside will have higher energy requirements. However, many other dogs will get less exercise in the winter and may need their calories reduced to avoid weight gain." A Texas A&M veterinarian made a similar point: basic calorie needs do not change with the weather, but a pet may need more calories if it is more active in cooler weather.

If walks get shorter in winter, check the portion against your dog's weight and activity with the dog food calculator, and see how to tell if your dog is overweight.