As days grow shorter and the coldest part of the year approaches, understand that your furry friends’ furriness will not always suffice to keep them safe and comfortable.

Hypothermia and frostbite are just as dangerous to dogs and cats as they are to humans, and perhaps harder to detect because we can’t always know what they’re feeling or thinking. Certainly some dogs are better suited to cold weather—those with thicker fur coats, and larger dogs in general—but no dog should ever be left outside when temperatures near the freezing point. Chihuahuas and pit bull terriers, two of the nation’s most popular breeds, are usually quite shorthaired and therefore especially susceptible to cold.

Sweaters, sweatshirts, and raincoats for dogs, therefore, are not just endearing, but sensible things to have on hand. While some dogs have no tolerance for foot coverings, many can grow accustomed to them—and dogs who will be walking in cold or wet weather may walk longer and happier with booties snug on their paws.

Most importantly, bring your animal friends inside when the weather gets cold. How cold is too cold? If you wouldn’t enjoy being outside without a coat or a campfire for hours, chances are good that your dog wouldn’t either.

Our cultural awareness of the dangers of leaving dogs in hot cars has improved significantly, to the point where many jurisdictions have made it legal for civilians to rescue dogs at risk of overheating. But because of the widely held assumption that their “fur coats” or a car’s enclosed space will protect them, we still too often leave dogs in uncomfortably cold cars.

Leaving a dog alone in a car for any length of time is never ideal, but if you do, remember that your dog won’t be able to tell you how cold they got while you were gone. You could be putting more than just her comfort at risk.

Cats present a different cars-and-cold-weather consideration. Because automobile engines can be a source of warmth well after a car is parked, outdoor cats and other creatures have been known to climb in under the hood. Obviously the spinning fans and whizzing belts in a car’s engine compartment with a cat resting too close would be significant health hazards, and many cats have been severely injured or killed in this way. A thump on the hood or quick honk of the horn before starting the engine could save a cat’s life.

Keep your animal companions cozy and comfortable this winter. They will surely return the favor.