Winter mode

"Winter mode" is a new (randomly occurring) map type for Minecraft Alpha. It was added on July 9th of 2010 and has a few unique properties.

Differences
The first of them is falling snowflakes. These snowflakes will create Snow tiles. Snow will "grow" on any tile that is directly exposed to the sky. Unlike Grass, Snow will not "grow" onto tiles under cover. You can place a torch/fire next to it in order to "melt the snow".

The second unique property is that of Ice. Ice is simply a river tile that is a solid block instead. You can destroy this block to create a river tile, or place a torch/fire next to it in order to melt it into water.