Now, years ago, there was no such thing as clothes for dogs, and there were yorkies years ago, so, it's more for show than anything..I have seen the smaller yorkies shake more often, because they're so tiny, my 14 lb one is always hot(just like me)..I have 4 little dogs(3 yorkies and a shih tzu), they go outside every night to run, with nothing on but their hair..
Guess you have to decide if you want to dress them up or not, the choice is yours..I do have a little cheap coat I bought for the 14 week old yorkie, I put it on her one night when I sat outside with her, but, now that she's out there running with the other 3, I leave it off her..