Originally posted by Bored Peon:

You can see this sort of thing all the time along the edges of mountains where the snow is in other biomes. The snowy area extends farther than the edge of the biome.

Most of the time you just see forest that is snow covered.

Yeah, I've a farm in the snow biome that has a sliver of the plains biome sandwiched between it and the black forest biome. Its on the slope of the mountain so I had to terra-form it into a terraced farm with spots showing(and growable) as plains on the map but with snow showing actually on the ground itself.