From Syria to the Confederate South, from Scandinavia to Vermont. From the current events that make the news, to the narratives that make their histories. It's difficult not to notice. Everyone loves warm sunny weather.
You can tell, by how it makes them go crazy and kill each other.
Summer weather makes people more hostile. Hotter climates seem to suffer plagues of violence that go on for centuries. In the US, northern states have more universities, while southern states have more prisons. Temperatures are rising globally, but wealthier nations are seeing declines in crime rates - we have more air conditioning than ever before, even amongst our impoverished.
Pervasive even in our language is the concept that temperature and emotions are related, yet it's rarely discussed. It sounds unserious. A novel idea, that surely can't have all that much merit. It doesn't feel as though it could possibly be that simple, despite an overwhelming body of data.
While it's probably not quite that simple, I do suspect it to be more straight-forward than theories about people being desperate for water, or attempting to migrate over each other. Rationalizing some instances, while being irrelevant to many others. Such explanations broadly fail to account for what appears to be a pretty much worldwide trend. Cold weather also leads to scarce resources, inclinations to migrate, and certainly discomfort, but people seem far less likely to kill each other over it.
I've always favored icy winters and northern woodland, myself. Maybe I'm biased by this. Or maybe, being the chronically self-conscious sort that I am, this is precisely why I'm biased. In my own life, from Louisiana to Minneapolis, I've noticed how different climates make me feel. Could also be related to the way my negative emotions tend to be channeled inward. When I get angry, I'm far more likely to hurt myself than anyone else, so it could even be an acute measure of self-preservation that makes me so opposed to moving somewhere that would have that effect on me.
Someone who isn't quite so likely to get bogged down dwelling on their own feelings or beating themselves up, might be more likely to move south. Me, I'd rather move to Canada or Sweden.