A map with snow.
Winter Mode was a randomly occurring map type for Minecraft Alpha. It was added on the 9th of July, 2010 and was the first "biome" to appear in Minecraft. Maps with the Winter Mode theme could not be converted back to normal worlds and vice versa without the use of third-party programs. Players could, though, force their savegame into/out of the Winter Mode by activating/deactivating the "SnowCovered" parameter in "level.dat" using a map editor. The Halloween Update disabled Winter Mode by introducing biomes. Since then, snow has appeared in the Taiga and Tundra biomes. Although behaving somewhat like a present-day biome because it altered the environment, at least one important difference between Winter Mode and the post-Halloween Update snowy biomes occurred: While Winter Mode affected entire worlds, snowy biomes only affect small parts of it. The Halloween Update disabled the snowfall effect and made Winter Mode obsolete (although now they have reinplimented snowfall) because snow is now area-dependent, as one of many biomes.
Differences between Winter Mode and the normal map type
One of the differences was snowflakes, which fell constantly. There were four different kinds of snowflakes. These snowflakes would create Snow tiles on any block that was directly exposed to the sky, provided that it was solid. Snow tiles which were hit by a light level of 12 or brighter (sunlight ignored) would melt. Snow could be broken by hand or with tools, and a shovel could be used to produce snowballs (at a rate of 1 per tile), which could then be thrown with a right-click or crafted into snow blocks. Snow would automatically disappear if a block was placed on it. It would also hover in the air if placed over a half block
The second element unique to the Winter Mode was Ice. When a map was generated, all exposed water blocks would be frozen into Ice, which is semi-transparent and slippery. Ice could be changed back to a water spring by breaking it by hand or tools, pickaxes being faster. Upon destruction, ice would not yield any item. Like snow, it could be melted by being hit with a light level of 12 or higher (sunlight ignored).
Also, animals would not spawn as much as in the normal world type.
See also