All it takes, is snow drifting in over the winter and no sunshine, until long after about everything has been melted off.
There's a dirt road not far from camp, over in Steuben Co. NY. When my cousin had a farm over there, snow would drift off'n the fields and close that road at least once or twice a winter. Because one spot in the road was a good 50' lower than the fields on top of the ridge.
Finally, back in the early 70s, they cut the bank way back from the road, so the snow wound up at the bottom of the bank, not so much out on the road.
One Easter we went up to camp when my son was about four or five, we'd had a warm spring. Temps were in the mid 70s at camp. Told my son I'd take him over and he could stand in some snow. Parents looked at me like I'd lost my mind.
Drove up that dirt road, knowing there would still be some snow at the bottom of that bank where the sun hadn't hit it yet. Snow was covered in dust, kid said where's the snow? Kicked some dust off and stuck him feet first in about two feet of snow. Even deeper back against the bank.
He made some snow balls, threw 'em at my parents when we got back to camp, told 'em the snow was right where I said it'd be.