Only 3 types of dogs need sweaters or coats

That's interesting and I agree with the fact that those 3 types could need coats. However, I think the dog will pretty much tell you if it needs some extra warmth. My little Yorkie doesn't need a coat in sub freezing temps, according to her. lol She hates wearing clothes.

Need is subjective to exactly how far below freezing is it, how much hair/fur does the pup have, and how long are you keeping the pup outside?

If I had a Yorkie in Alaska, I'd never let her out without a coat in the winter. Down here in Alabama...that's a different story.