The White Witch who has declared herself Queen of Narnia cast a spell over the country, which means that it is always winter but never Christmas. Since both the protagonists and the primary audience for the book are children, this conveys an idea that the single most exciting and joyous event associated with winter is missing from that season of cold and darkness. As the children and the beavers journey towards Aslan, the Witch's power is shown to be weakening both by the snow melting in the increased warmth, signaling the coming of spring, and by the advent of Father Christmas, who confirms the meaning of his own arrival:
"I’ve come at last," said he. "She has kept me out for a long time, but I have got in at last. Aslan is on the move. The witch’s magic is weakening."
Father Christmas also gives the children presents, which they use to fight for Aslan and against the witch. Peter receives a sword and shield; Susan, a bow and arrows, and a horn to call for aid; Lucy, a dagger to defend herself, and a bottle of cordial with powers of healing for those wounded in the battle.
In his autobiographical work, Surprised by Joy, Lewis used the thawing of snow as an arresting image of his doubts about Christianity melting away. The Christian message in the Narnia books is never far from the surface, and it may be that Lewis has a similar idea in mind here, as the coming of spring coincides with the symbol of Christmas in foreshadowing the imminent defeat of evil.