The changelog for snapshot 15w14a says that rain was removed, but it still occurs in a many biomes, complete with the rain particles texture and the sound effect of rain hitting the ground. I was not able to test every biome, but examples of biomes that are affected include plains, forest, and ocean, while an example of an unaffected biome is extreme hills. However, regardless of the biome, snow still accumulates on the ground as if it were snowing.