You can grow cold weather crops in a greenhouse with no heat even in a climate like that. Stuff like winter lettuces, spinich, etc. It will be quite hard to grow much else reliably in a place that sees sub zero weather on occasion even in a green house.
Provide heat at night with a small heater (be safe) just a bit of heat will go a long way.
Put in some drums of water painted black they can act as a heat sink and give you some additional heat retention once the sun goes down.
I am not real up to speed on green houses in such cold areas, best bet would be to find someone in your local area that does it and share what works, does not work, etc with them.