When it comes to nature-made protection against the elements in cold weather, some dogs are better equipped than others. Dogs come in all shapes and sizes, with different hefts and types of fur, all of which can influence how powerfully the cold affects them. Some dogs simply have more insulating body fat than others. Your dog’s capacity to stay warm outside in the winter depends on his breed, his size, and his age. But in the end, the biggest determining factor for whether your dog needs a jacket is your best friend himself. Read on for signs that your dog needs help from the bitter cold and other situations where wearing a dog jacket is crucial for his health and well-being.

Dog Jackets 101

A jacket may seem superfluous for your big, hairy dog and it probably is. Nature has prepared some breeds for even über-cold weather with their own ample coats of insulating hair: the Siberian Husky, the Malamute, the Saint Bernard, and the German Shepherd are examples. If you have one of these or a dog of its ilk, and he’s young and healthy and possesses a beautiful coat, he does not need a dog jacket.

But the Chihuahua, the Greyhound, the French Bulldog, and many terriers and pinschers are examples of vulnerable breeds: it’s possible these doggies are as uncomfortable outside in winter as you’d be if you ventured out naked. Lean, short-haired breeds simply have difficulty generating and retaining heat on their own and would welcome an insulating, waterproof dog jacket on cold days. And dogs whose bellies are close to the ground—the Dachshund and the Corgi, for example—need extra protection from frigid sidewalks and snowy paths. Toy and small breeds, light-bodied breeds, and breeds with very short or thin hair (even if it’s long by nature but you keep it clipped close) need the extra warmth of a dog jacket or sweater outside in the cold.

A dog coat or jacket in winter also benefits these canine populations:

• Senior dogs
• Puppies
• Dogs who are ill
• Dogs whose hair growth is impaired by disease (Cushing’s or hypothyroidism, for example)
• Dogs with diabetes, kidney disease, heart disease, or hormone imbalances
• Dogs with less responsive immune systems
• Dogs recovering from an injury

And what of the indoors? The same vulnerable breeds who enjoy the added warmth of a dog jacket outside will appreciate an indulgent dog sweater or blanket inside if the thermostat is routinely kept on a low setting. And if your companion dog suffers from arthritis, he’ll appreciate the warmth and comfort of an insulating dog sweater all the more.

How To Measure For A Dog Coat

Make sure your dog is standing; take the circumference of the neck and the widest point of the chest. Then run the tape measure from the collar to the base of the tail. Knowing the dog's weight is also helpful. This information will help guide you when you select a jacket for your dog, but you’ll also need to see it on her to know if it’s a good fit.

A properly fitted dog jacket should cover her neck and belly if it is a full-coverage style (make an allowance for a male dog). The fit should be snug but not tight, and the jacket should reach to the base of her tail. An easy-on, easy-off design is best—avoid a tight jacket you must pull over her head, or any design that is a struggle to get on. When she is wearing her jacket your dog should enjoy freedom of movement at the armpits and around the neck, and be able to move freely.

Dog Fashion Sense

Your dog will undoubtedly look fetching to you in whatever jacket you choose, but the only thing she’ll notice is whether she’s comfy and cozy. So what’s the best material for dog coats? Wool may be warm, but it’s also itchy. Above all, it can be difficult to wash; a poly blend is a better choice. If you live in a snowy or wet-weather region, choose a water-resistant or waterproof dog jacket. And a fleece lining sweetens the deal: it’s warm and comforting.

No dog jacket or coat should have parts she can chew off and swallow. Look for zipper-less designs free of hooks, buttons, or tags.

Let your dog wear the jacket inside at first to get used to it. If the dog hates it, all bets are off: try a new jacket. Once you settle on one that seems to work, monitor for any spots on the body that suggest the jacket is rubbing the wrong way—literally. You’ll need to start over with a different dog jacket if you find any.

Note: a dog who is uncomfortable wearing a jacket should never be forced to wear one.

When To Avoid A Dog Jacket

The American Veterinary Medical Association recommends a jacket in the cold for any dog weighing ten pounds or less. Regardless of your dog’s size, shivering is a clue your dog needs extra protection. In some instances, however, putting your dog in a coat puts his health at risk. If his own coat is too thick and heavy, he can overheat. Pay attention to your dog—excessive panting, scratching at the jacket, or even a general lack of enthusiasm about wearing it can all be signs of overheating.

Other factors can help you decide whether to dress up your dog: his level of activity, how sunny it is, and even his hair color. If you and your black Labrador Retriever are striking out for a run on a cold, sunny day, he may not need a coat at all: his dark hair will absorb the sun’s warmth, and the workout will leave him sweating in no time.

On the other hand, your outdoors-y dog—even if they're an athlete supreme—may need protection on a snowy hike, particularly when you’ll be hiking through deep snow. Your dog will benefit from a coat or jacket that offers belly coverage. Even in the absence of snow, keep an eye on your dog; if she appears uncomfortable at or below a particular temperature, put a fleece coat on her to keep her core warm on the trail and in the tent at night. If you anticipate cold rain, find a warming coat that resists water and blocks wind.

Knowing when and how to dress up your dog is about more than the occasion. Sometimes a dog jacket just makes sense. Listen to what your dog is telling you—it may be too chilly to go on a wintry walk without some extra coverage. Take your cues from your dog; maybe a comfy dog jacket is just the thing to keep them safe and warm.