How to tell if your dog needs clothes
Dogs come from the wolf family, which itself originated in Siberia, and hence they originally had long hair the way Siberian huskies do. The fur was thick enough to make sure they survived the coldest winters intact.
However, ever since the fad for breeding dogs emerged a couple of centuries ago, modern dog breeds are far removed from their wolf ancestors. You can get breeds like whippets and the Mexican hairless which are bred for warm climates, and hence have short or very little fur. Breeds such as these can find coping with cold winters difficult especially when taken outside of the house for a walk.
Of course it all depends where you live, and clothes for dogs do not arise at all if you live in warm climates.
When deciding to get clothes for your dog, first observe how it copes when out walking. If your dog is reluctant to go outside and shivers or shakes, it has a problem with cold and would benefit from a loose dog sweater or a dog snuggie to ensure it doesn’t lose too much hear.
Conversely, if you dog starts panting a lot it is a sign that it is over heating and you need to remove any dog clothes it is wearing. Finally, I would hesitate to put clothes on a dog that had long hair – it’s long fur should keep it protected, and restricting it with clothes will make the dog too hot and uncomfortable.