Snowfall

Deep snow on the winter ground in the enhanced outdoors, thicker in the wild than in towns: it builds while snow falls and melts in clear weather, and you, foes and townsfolk leave tracks that fill in over time.

Snowfall is an entry in the Built-in mods database, listed under On.

Several of these change core rules, so the guide pages describe the game with them on. 'Fixed by the room' means online everyone plays with the mod at its shipped settings, whatever they choose offline.