I have 10 years experience hunting Canada (Alberta, Sakatchewan) in mid November through early December and I have learned a few things staying out all day in up to -35 F.
Wood stocks expand and contract as they are heated to room temperature and frozen in the field daily which can cause your point of impact to change. If all you have available is a wood stocked rifle, keep it cold. Synthetics do not expand and are the best choice in the frigid elements.
Firing pin freezes can also be an issue, ensure there is zero oil or grease around your firing pin. A gunsmith can help you before your trip. Unload and do some dry fires mid-day just to be sure if it's real cold. Overly greased components anywhere on the rifle can be a probelm too, like safeties, etc.
The rule of thumb with most temperature sensitive powders is a loss or gain in velocity of 2 feet per second per degree of temperature change. Most factory velocities are clocked at +70 F. If you do your own chronographing, take a thermometer. If the temperature is 90 degrees, your bullet's velocity will increase about 40 fps over what is was at 70 degrees. Likewise, at 20 F, your bullet's velocity will decrease 100 fps over baseline at 70 degrees. At 300 yards this means very little, at 500 yards, this difference can be significant. Hodgdon extreme powders are temperature insensitive; most of my use has been with H4350 and H4831, and I verified this via chronograph. The tradeoff in my barrels seems to be a little less accuracy than the DuPont brands of 4350/4831 that are temperature sensitive.
Have some wipes for your scope and binocs, you'll fog your glass quite easily with your breath in frigid cold.
I hope this helps.