Hi, just saw your post!
Sweet potatoes need a long growing season... I think most of them are well over 100 days, plus they like hot weather. I tried growing them one time and of course it turned out to be our coldest summer on record (or at least it seemed that way). If I tried them again I would definitely grow them inside a "low tunnel" to extend their season and provide additional warmth.
On the upside, the vines and leaves are edible, as well as the tubers