the eternal winter

a storm of purest white flies across the world putting the world into an eternal winter for a year with temperatures averaging out at -3 degrease Celsius waters frozen over, normal crops find it hard to grow but certain types of plants and animals thrive. when the storm is summoned everyone in the world takes 5d6 frost damage and takes takes 1d4 frost damage for every hour that there without shelter or warmth. when the winter is formed, those who can cast ice knife can summon blades of ice to rain down or specific targets (+3 to hit, 6 targets, 3d8 + 4 frost damage), if you cast any fire spells they will do half the amount of damage no matter what, but frost spells or wind spells do twice the amount of damage and have twice the range of their original range.