Do you mean Fahrenheit or Celsius? That is ridiculously cold if it is Fahrenheit. On second thought I just looked it up and it is celsius which kind of exciting to me. I am in a similar predicament, but I live in a place a bit warmer than you. I have found a surprising amount of interesting plants that I can grow outside:
Ipomoea violacea/tricolor in the summer
Solenostemon scutelarioides/plumei in the summer
Petunia violacea in the summer
Salvia divinorum (outside in the summer and indoors in the winter)
Scutelaria laterifolia/galericulata
Acorus calamus
Datura/Brugmansia
Lobelia inflata
Leonurus sibiricus
Hieracium pilosella
Nicotiana rustica
Phalaris aquatica
Phalaris brachystachys
Desmanthus illinoensis
Artemesia absinthium
Verbascum blattaria
Nepeta cataria
You should be able to grow these plants too with a little bit of work. Most of these plants are mildly psychoactive, unexplored, or take commitment to get them to work but that's the price of living so far north. A lot of these are weedy northern species which is a plus when gardening in the north. I might add to this list as I am sure I have forgotten a few or maybe many. I also omitted some plants as I am not totally sure about what you mean by "useful".
Maay-yo-naze!