Snow Mod (Discontinued as of 1.6)Download: See Download Page
Warning: This mod is very resource intensive and marginally unstable. There are config options to control height of snow and update/growth rate. The only way to remove the snow is with a program like MCEdit.
Description: This mod adds a custom snow block that, when snowing, will grow. On new World/chunk generation it replaces all vanilla snow with the exception of on leaves and wood with the new snow.
There is a config option to enable snowing in all biomes. In order to accomplish this it was required to change the biome temperature resulting in mechanics that rely on temperature, such as tree colour to deviate from the expected norm.