When playing some pre-1.7.2 worlds I made, I found that it was raining in my older Cold Taiga biomes. While I guess this is caused by the game believing that the pre-1.7.2 Taiga biome is the new post-1.7.2 Taiga biome - where it rains instead of snowing - due to the old biome being labeled only as "Taiga", this is an issue that is screwing up my pre-1.7.2 maps.