We live in MI as well, and I've been debating whether or not to buy my 13 week-old pup a bigger sweater for this fall/winter because she loves being outside, even when it's soo cold! I put a sweater on her a couple weeks ago on a particularly cold day, and I received looks like I'm one of those awful people that dresses their dogs up for fun :/ I suppose a general rule of thumb would be if she's shivering, dress her up-- despite the looks!
. thanks everyone for the help.