Snowfall

Snowfall is a type of weather that occurs occasionally in Minecraft.

Behavior
Snowfall is a temporary, biome-specific occurrence that can happen randomly at any time in snowy biomes. In stony shore and windswept hills biomes, snowfall only occurs above layer 120. In taiga and old growth spruce taiga, snowfall occurs only above layer 160. Snowfall occurs above layer 200 in old growth pine taiga. Snowfall also occurs in frozen ocean biomes, where it only occurs in certain locations, while it rains in others, as a result of a temperature gradient within the biome. In lush biomes, snowfall can occur only at layers above the block height limit. Snowfall does not exist in hot/dry biomes and in other dimensions.

Below are the altitudes at which rain ends and snow begins, depending on the biome. The exact height of the snow line is randomized: take taiga for example, the lowest possible snow layer forms at y level 153, and the minimum height where snow forms at all locations is y level 168, with snow lines ranging between y levels 153 and 168 across different locations.

The average snowfall lasts 0.5–1 Minecraft day, and there is a 0.5–7.5 day delay between snowstorms. Snowstorms have a small chance to worsen into thunderstorms.

Thunderstorms can be skipped entirely by sleeping in a bed.

Effects


Snowstorms darken the world, causing the light from the sun to decrease by 3, bringing it to light level 12 in full daylight. Moonlight, however, is not reduced, and remains at light level 4. The sky itself darkens, even in biomes where it does not snow, and $$, celestial bodies (the sun, moon, and stars) are no longer visible. $$, the sun and moon are still visible in biomes with no snow. The clouds darken from white to a light gray, but they do not precipitate. While the sun is not visible during snowfall, the glow associated with sunrise and sunset is still visible.

As it snows, snow layers regenerate over all blocks with a solid top surface at integer y-values. $$, these snow layers accumulate and grow over time, until the accumulated snow makes a snow block and removes it self, repeating the cycle. $$, snowfall creates one layer of snow by default, and the number of layers that can accumulate can be altered by the game rule : setting it to makes no snow form at all, and setting it to  or above lets snow form up to the level of a full block.

Snow particles
Falling snowflake particle effects are visible through the air over all cold regions during snowfall. Unlike with rain, any entities that are on fire are not extinguished on contact with snow. Snowflakes fall in the two middle lines of a block; they do not visibly fall directly onto the player.

Powder Snow
During snowfall, cauldrons under the sky slowly fill with powder snow.

Trivia

 * Snow actually falls one block into the void (Layer -1). This can be seen by digging a vertical shaft down in Creative mode, removing the bottom layers of bedrock, and flying down into the void. Note that no particles are emitted from the snow, due to the absence of a block below it.
 * Snow still falls above the clouds. Notch's explanation is that the gray above the clouds during a storm is another layer of clouds and the origin of the snow.
 * There is a never ending snowfall above a certain Y value due to the temperature gradient within the biome.
 * At extremely high Y values, snow appears to fall more slowly and the texture of the snow particles becomes vertically stretched. The slowed falling speed becomes noticeable at around Y=200000, while the vertical stretching effect becomes noticeable around Y=1000000