For all the time we spend inside the warm, colorful chocolate factory, it would be easy for us to forget that in the outside world, it's the dead of winter. Not only does the snow pile up around Charlie's tiny two-room house, the freezing wind comes right into the house, leaving no escape for the Buckets. Of course, this means, "The excitement over the Golden Tickets had long since been forgotten. Nobody in the family gave a thought now to anything except the two vital problems of trying to keep warm and trying to get enough to eat." (10.4)
That cold weather only increases their appetite. The narrator reminds us that in the cold, "Most of us find ourselves beginning to crave rich steaming stews and hot apple pies and all kinds of delicious warming dishes" (10.5). But the Buckets don't have any of that. So the cold both adds to their troubles and makes their troubles even more obvious to us readers. Winter is not a fun time to be poor and hungry.
Thank goodness for the chocolate factory, then. Once inside, Charlie whispers, "How lovely and warm!" (14.25). Sure, there's a practical reason the factory is kept warm, which is that Mr. Wonka's "workers are used to an extremely hot climate," (14.21), but the warmth of the factory has a greater effect on the story. It's a stark contrast from the cold Charlie's been experiencing, and it highlights just how unfortunate the Bucket family's circumstances are. Plus, this contrast makes the ending all the more sweet.
Can Charlie avoid winter forever, though? Probably not. That snow pops up again during his exhilarating glass elevator ride with Mr. Wonka and Grandpa Joe: "Looking down through the glass floor on which he was standing, Charlie could see the small far-away houses and the streets and the snow that lay thickly over everything." (28.26).
This snow's a bit different than the snow that piled up around their house, though. In fact, viewed from such a great height, this snow is almost downright picturesque. It must feel good for Charlie to know that he'll never have to sleep on the floor and have that cold wind blow inside his walls again. For Charlie and his family, winter is definitely over.