Snow

Snow is a cover block that is found near Ice Plains and Cold Taiga biomes. Snow can be removed like any other block. Placing a light source will cause snow around it to melt and will prevent them from regenerating during snowfall. Snow melts in the same pattern as ice.

If the snow is on a grass block, the grass will turn white. This does not affect grass growth. Snow will not damage tilled and hydrated field areas, nor will it protect those plowed fields from being trampled on. Gravity-affected blocks like sand and gravel will not fall if the block below them has snow on it.

Destroying snow with a shovel yields one snowball, which can then be crafted into snow blocks or be thrown. If it is destroyed with anything other than a shovel, nothing is dropped.

If snow forms on top of a cactus, the cactus will still cause damage when stepped on or touched. Cacti cannot grow if there is snow on top of it.

Snow will not form on top of glass, slime blocks, ice, piston, glowstone, slabs or stairs or any other transparent/light emitting blocks.

Snow melts near light sources (except sunlight), up to 3 blocks from lava and glowstone, 2 blocks from torches, and it won't regrow 2 additional blocks away.

Snow can be collected in large quantities through snow farming.

Snow can be stacked to a full block beside a cactus without destroying it.

Trivia

 * The "topSnow" block's thickness is based on its data value.
 * As of Beta 1.9 pre5, the top of Grass' and Snowy Grass' textures were slightly changed.
 * A Snow Golem can be used to generate an unlimited amount of snow without the need to explore more land or wait for snowfall.
 * The snow and wool sounds are actually slightly different.
 * Attempting to place torches on snow will replace the snow with a torch.
 * Snow on a block of soulsand makes the soulsand act like a normal block
 * Snow layers 2-7 prevent hostile mobs from spawning
 * Lighting fire to a block of snow created by stacking snow covers will create the same effect as would lighting a hopper, the fire will be invisible
 * TNT cannon designs that involve slabs can be aimed much more accurately using different layers of snow cover rather than a slab.
 * It's possible to create a one-way gate by placing double layer of snow under the doorway and in front of it.
 * Floating snow is usually caused by lakes or lava lakes removing the block below the snow when creating an open spot above the lake. In previous versions when you could fall through floating snow the lava lake/floating snow combo could be a vicious accidental deathtrap (though rare). The lava lake will eventually melt the floating snow, but not until a minute or two after it's first spawned upon the player entering a new area.
 * Snow Golems can't be created by two fully stacked snow covers, possibly because they have a different code than regular snow blocks.