That depends on what kind of clothing we are talking about. Some do wear coats especially made for dogs during the cold seasons and during winter.
While other dogs are conditioned to wear anything (just like grooming)... especially since this is added attention from their owners and probably more treats. I have a Corgi friend who loves dressing up. And as soon as he sees these new clothes, he would excitedly get up his couch because he knows this is another picture session with his "Mom". And she's not making it up, she videoed herself and the Corgi preparing for a photo shoot. He had his nub of a tail wiggling.
I used to make my dogs sweaters but since it's a summer and the sun is blazing almost everyday, there's no point making them wear it.
