I live and hunt/shoot in Eastern NC at 150'-200' above sea-level. This November, I am going on my first trip to Alberta Canada to hunt whitetails. Elevation will be somewhere around 1900' above sea-level and temperatures could be from -20* to 20* (Hopefully). How will this affect the way my rifle shoots? Faster or slower? Point of aim to point of impact? I will be taking my 300 win mag and shooting 180 grain Nosler Accubonds.