Actually, winter is real. The series takes place on a sort of "counter-earth", and for some reason the seasons last for years. So while they have just enjoyed a summer that lasted several years, autumn has sped by, and now they are entering winter - which could also last for years.

The big problem is that the war has damaged so much of their farmland and industry that they do not have enough food set aside to prepare themselves - well that's one problem in addition to all of the others.

So, yes it is about being prepared I guess, but it is also about a real situation that happens every decade or so.
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