Minecraft wiki entry for Things_not_to_do, associated text: Because of the fact that snow layers count as a block, any snow layers next to the bed a player slept in may result in the player waking up standing on their bed, and chancing waking up inside a block if the player's ceiling is only 2 blocks above, which may result in suffocation damage to the player. The player may also not respawn at their bed if they die, because it is obstructed. To avoid this, keep Snow Golems away from player beds. Also, if the player must sleep in a snowy biome, the player should remove any nearby snow blocks.