You can see snow through walls/ in your inventory and it really bugs me.
A way to make it happen is simple.
1. Build/Face a block, building or wall.
2. Drop a item.
3. Pick up the item while looking at the wall/in your inventory.
Done. You saw snowflakes through the blocks.
I think its been a bit of a problem since 1.7.10 but I have no way of recreating it in 1.7.10 and below.