Board Thread:General Discussion/@comment-35695595-20180527031600/@comment-35704330-20180527140651

They have snow in Snowdin and rain in the Waterfall because the roof is super high. So the water coming from Waterfall flattens in the air and perhaps forms clouds, and these clouds can actually float to Hotland and Snowdin, but because Hotland is so hot, so they can't actually rain or snow in there... And in Snowdin, I think somehow they can have super cold weather so these clouds can snow. I saw someone explained this in Steam Community.

(Alphys said there was no weather down there cause' she lives in HOTland, it's just HOT, nothing else, and probably she never visits Waterfall or Snowdin)