Well winter is a noun so if you mean appopriate adjectives then, cold, bitter, dark, breezey, chilly, wet, wild, unpredictable, sharp, icy, dangerous, extreme, changeble, hibernation are all possiblities. Hope this helps!
A few words to describe winter: Algid, biting, benumbed, frore, gelid, hawkish, hiemal, hyperborean,rimy, shivery, boreal, inclement, sleety, stinging, and numbing.
