A dependent clause should have no punctuation between an independent clause when the dependent clause comes afterwards.
In the poem, the setting is never clearly stated, but based off some of the lines in the poem, we can make an inference that it happens during a clear night.
Most likely metaphor..... but I could be wrong
Answer:
Literally, it means that it is snowing.
Metaphorically, it could mean that something delicate looking yet sturdy has been moved and positions in a situation have changed.