It's a byproduct of the naïve belief that climate change means it gets hotter (and little/nothing else), to which "just move north" is a logical conclusion. The truth is closer to climate change means more extreme weather happens everywhere, and things get hotter up until -- and here's where my knowledge of science may be much less up-to-date -- a critical mass of ice at the poles melts, and which point the temperature plummets.

By definition a lot of areas will be hit hard and some areas will be hit less hard but it's not going to be along a north-south axis.