'Snow' is PIE *snoygwhos — Latin 'nix' is the same word minus the initial s-. One of the widest IE cognates.
Atmospheric water vapor frozen into ice crystals that fall in light white flakes.
From Old English 'snāw' (snow), from Proto-Germanic *snaiwaz (snow), from PIE *snóygʷʰos (snow), from the root *snéygʷʰ- (to snow). This root is one of the most widely attested in the Indo-European family, appearing in nearly every branch — Latin 'nix' (genitive 'nivis'), Greek 'nipha' (snowflake), Old Irish 'snechta,' Sanskrit 'snéha-' (oiliness, originally stickiness of snow). The initial *sn- cluster has been remarkably persistent. Key roots: *snéygʷʰ- (Proto-Indo-European: "to snow").
Latin 'nix' (snow) lost its initial s- — a regular sound change where Latin dropped the 's' before 'n' at the start of words. This means Latin 'nix' and English 'snow' are the same PIE word, but Latin shaved off the first letter. The same s-loss explains why Latin 'nāre' (to swim) corresponds to Greek 'nein' and not to a form with sn-.