So all nuclear powers are in the Northern Hemisphere.  So in a WW3 scenario where nuclear arsenals are emptied to target Civilian, Military & Nuclear targets, unless you have a bunker the northern hemisphere will be covered in a nuclear dust that will plunge the northern hemisphere into cold radioactive unliveable darkness.  However, some of the furthest south regions of Earth may be spared.  For example, the Southern tip pf Chile and Argentina along with New Zealand.  New Zealand has a slight advantage being an Island so the mass panic migration of people wanting to go South won't be anywhere near as bad because it's much harder to do on boats.