Slimes spawning in wrong locations

Slimes are spawning above ground in Snow Biomes, Forest, Extreme Hills areas...perhaps in or near water. Perhaps related to this is I have a HUGE underground mined area below the area I seem to see the slimes. Basically, I have mined a 3 block-high area above bedrock, with a ceiling, another 3 block-high area mined out, with a ceiling, and lastly another 3 block-high area mined out extensively in all 4 walking directions below ground. Slimes do spawn a lot down there but that is expected. However, it was not expected to see slimes above ground in the snow biome.