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.
Duplicate of MC-31205 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.