the rain in waterfall i get because of the waterfalls, but how snow?

Oh my god
I never thought of this

It doesn't need sky for rain in waterfall sonits the same in snow din but it's cold

*ahem*
✨Magic✨

In a large enough underground space, it's possible for snow and rain to naturally occur.

mt ebott is cold and rain gets frozen into snow, and waterfall is just an underground hot spring.