One of those little things --- I've got a bunch of old forest reindeer tracks nearby my cabin from mid-autumn. Seems very odd that months later, when everything's covered with a foot of snow, I can still see them fine.
Making snow cover tracks (and maybe rain decaying tracks?) would also make the weatherlore skill a little more useful. Hunting during intermittent snow would be very difficult, since you couldn't keep a track on as the snow covered things up. Hunting after the snow fell on a clear day would be your goal.