What rare event occurs on the island in Chapter 12 and what plotline develops from it?

In Chapter 12, it begins to snow, an event which the narrator states has not happened on the island for at least ten years. As time goes by, it begins to seem like the snow will never stop falling and that winter has arrived permanently. The permanent arrival of winter is a symbol of the way in which the island is slowly dying as they lose one object after another to disappearances enforced by the Memory Police.