In an early episode of Conlangery they discuss the "bignum words for snow in Inuit/Eskimo languages" myth. While this is glossed over, they do go on to mention that at least one language in the general region (I forget which) has a verb-producing affix that, applied to a noun, means "to be freezing in one's ~".

So when you're satisfied with all of the purely functional derivations, you may want to consider something uniquely culture-bound; perhaps something not otherwise easily expressed with a simple verb.