I’m building a post apocalyptic world right. In my world, after the Nuclear War there is a brief nuclear winter.

Realistically, some have told me, the survivors would migrate south as the Southern Hemisphere would be less affected then the North. However, in my world this cannot happen under any circumstances.

See, the survivors in the North are supposed to be the ones who repopulate the continent of North America after WW3. If they leave off to Central America, there will be no one left.

What is a logical reason for survivors not to migrate south during a nuclear winter?

  • $\begingroup$ This question feels rather broad. There are a whole number of reasons why people today don't migrate south. Many of those reasons should still hold up during a nuclear winter. $\endgroup$
    – sphennings
    Apr 24, 2020 at 20:15
  • $\begingroup$ I'm not seeing the problem. If these people feel that much affinity to the north, they would make it their "holy land" and have all sorts of mythology built up around how they will go back some day. It would be a core component of their culture and it would impel them to migrate back to the north at the first opportunity. $\endgroup$
    – Futoque
    Apr 24, 2020 at 20:37
  • $\begingroup$ It could be as simple as they don't know that its "better" in the south. Migrating is a lot of work, people don't want to move unless they absolutely have to. I don't think its common knowledge that after a nuclear war that it is better to go South, you could easily say that the small number of people who knew that died off. Or maybe a few survived, but no one believes them. $\endgroup$ Apr 24, 2020 at 20:45
  • $\begingroup$ Why can't they flee...and then return after the winter wanes? $\endgroup$
    – user535733
    Apr 24, 2020 at 20:52
  • $\begingroup$ ... .didn't someone build some sort of wall? $\endgroup$
    – mcalex
    Apr 25, 2020 at 5:09

3 Answers 3


Make the south worse. Here are just a few reasons.

  1. Ashfall: A southern hemisphere super-volcano has erupted, and the global stresses from this drive the nuclear war. You might have your north American survivors fending off invasions from the south.
  2. Pandemic: A global disease outbreak pushes the nuclear war. Before the ball went up, North America nuked Central America to contain the outbreak. Sounds like a good reason for someone to hate the USA's guts.
  3. Global Warming: The south has become an uninhabitable wasteland of 130 degree weather, and maybe in a couple generations it will be better. Catastrophic climate change is one of the most likely things to trigger nuclear war.
  4. The Enemy: Either the south IS the enemy (a South American/expansionist alliance and a nuclear-armed unified Africa) or the war started with the enemy gaining control of the south by alliance or conquest; not a bad reason to start a nuclear war...

They wouldn't have to. Models for a nuclear winter after a large nuclear exchange predict a 36 degree Fahrenheit drop in the average temperature in some parts of North America for a few years. Significant parts of the USA, such as the south, would have average drops of less than 18 degrees Fahrenheit.

Average Global Surface Air Temperature after a nuclear war

While this is a lot- a 36 degree F drop in Chicago is equivalent to average -15 or -20 degree lows in January- it's not apocalyptic. A lot of people, especially in Russia, Canada, and Alaska, routinely live in much colder environments without having any nuclear wars. An -18 degree F temperature change in Austin or Dallas Texas still keeps the average temperature above freezing year-round.

To be clear: this is certainly apocalyptic from the perspective of the climate, agriculture, and biosphere. But if you just need a few hundred or thousand people to survive on canned food and peanut butter for a few years without freezing, that's eminently doable.


Rumors that American's moving south become slaves in the former third world. ...and badly treated slaves because everyone resents us for blowing up the world.


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