Snow

Snow (Snow Top in Pocket Edition) is a cover block that is commonly caused by snowfall.

Obtaining
Destroying snow with a shovel yields two snowballs, plus an additional one snowball per extra layer on top (meaning a three tall layer drops four snowballs). If it is destroyed with anything other than a shovel, nothing is dropped.

Snow will melt if there is a block light level of 12 or more. It will only melt from sunlight in Pocket Edition.

Natural generation
Snow naturally generates in ice plains and cold taiga biomes, and in the extreme hills biome above layer 95.

Snowfall
In snowy biomes or in cold biomes at varying layers, it will randomly snow instead of rain. While it is snowing, snow will generate on random non-transparent blocks with a block light level of 10 or less, with the exception of packed ice. In Pocket Edition, multiple snow layers are built up naturally during snowfall, and inside certain plants.

Snow golems
Snow golems generate a trail of snow in snowy, cold, and some medium biomes, or any non-dry biome in Pocket Edition.

Usage
If the snow is on a grass block or on mycelium, the grass will turn white. 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, and will break if they fall onto snow.

Pocket Edition
In Pocket Edition, snow can be placed inside flowers, mushrooms and tall grass, and will layer and mine normally. Snow is affected by gravity and will fall if unsupported.

Data values
A snow layer has the ID name  and is further defined by its block data. A snow layer also has a block state which is expected to replace the functionality of block data in a future version.

Trivia

 * Snow can be stacked to a full block beside a cactus without destroying the cactus.
 * Attempting to place torches on snow will replace the snow with a torch.
 * Snow on a block of soul sand makes the soul sand act like a normal block.
 * Snow layers of 2 to 7 thickness prevent hostile mobs from spawning.