i love fido fleece. it keeps them warm and dry. romeo has one on right now.
we live in nj and our house is 110 yrs old and no insulation. it's about 50 degrees outside and he is comfy in fido fleece. yorkies are single coated dogs so you need to keep them warm and protect their belly. check the link below for 30% off at sitstay.com.
http://www.sitstay.com/store/clothing/coats1.shtml