Winter, Snow
Snow lays a frozen blanket over the landscape. Nothing can grow or flourish when winter has arrived; everything is still and static. It has a paralyzing quality. A snowy landscape in dreams may thus refer to something unchanging, something static—perhaps an emotionally cold state. At the same time, it represents a time for rest and stillness before the energy of spring breaks through.
Frozen state
Winter, snow, and ice may symbolize the paralyzing coldness—either an emotionally "frozen" state, an intellectualized condition, or a situation stuck in a particular "mode." A snowy landscape is a cold environment and can, therefore, symbolize a situation devoid of warmth, relationships, and opportunities for growth. This may result from the repression of “the warmth.” One might recall Dante's depiction of the devil, frozen in ice.
Ice and snow share qualities with glass; a frozen landscape resembles the glass mountain of fairy tales. Likely, something must be freed from captivity.
Purity
On a more positive note, snow can be seen as cleansing, with its sparkling white color (cf. Milk). The name Snow White illustrates the girl's innocence and goodness, not coldness (cf. Glass, however). In this sense, snow for alchemists could represent the purified Mercurius in albedo (enlightenment).
Fertility
Winter itself is not inherently bad; rather, it is essential for fertility. The earth becomes fertile in summer, rests under a blanket during winter, only to become fertile again once the blanket melts away. Frost is necessary for certain plants to bear fruit; for instance, apple trees require a period of cold winter dormancy to bloom and bear fruit when warmth returns.
Jung dreamed three times in 1914 of an arctic cold spreading over the land: “All the land was empty of people, and all the lakes and rivers were frozen solid. All living greenery was paralyzed.” The third dream, however, “had an unexpected ending,” which connects to this symbolism:
“There stood a leafy but barren tree (my tree of life, I thought), whose leaves, under the influence of the frost, had turned into sweet grapes full of healing juice. I picked the grapes and gave them to the waiting crowd.” (Memories, Dreams, Reflections, p. 164).
Sleep-Wake Cycle
Just as Snow White sleeps to awaken into fertility, snow and winter in dreams may indicate a situation waiting to blossom; like a sleeping person needing her rest but destined to awaken.