There are, in fact, no seasons. It makes life interesting when trying to fit it into a more detailed and realistic setting. Especially since the fairy tale can knock off serving a blacksmith for seven years in order to get him to make something for you so you can cross the glass mountain in a sentence or two.
The characters don't have anything that bad, but they are traveling, and they don't have the technology to make winter a nuisance rather than a serious obstacle. Also, no less than three women get pregnant and give birth during the story -- in parallel, not in sequence -- but still, it locks some time periods down hard.
Using the winter as a reason to stop does burn up some time, so the factors do help each other -- sometimes.