Snow is never named in "A Winter's Day...", and that is the poem's best trick. Only the title hints at the season. The rest is left to a metaphor, snow as feathers, which the poem then keeps swapping for new ones until we watch the weather as if through a kaleidoscope. The central idea is that snowfall is a gift from above that is also a force. It brightens, softens and covers everything, but it also pierces, invades and refuses to be held in place.
The comparisons arrive almost one per stanza. Feathers become rivers ("Forming rivers of white, / Flowing to places far away"), then stars, then shards, then tiny cities, and finally hair drifting down from "singing angels." Each image changes what snow feels like. Rivers suggest movement and scale, "Enveloping entire lands." Stars suggest light against darkness. Cities suggest accumulation, as flakes pile into drifts that look like rooftops. The angels in the fifth stanza make sense of the opening image, since feathers falling "from the heavens" are, in the end, shed from angels' wings.
The poem is more interesting where its images pull against each other. In the third stanza the flakes are "Plummeting from dark space, / Like helpless, sharp shards." "Helpless" asks for pity, "sharp" asks for caution, and the line holds both. The fourth stanza is stranger still: the cities are "Infested with lenient cotton." "Infested" belongs to pests and plague, while "lenient" means merciful and "cotton" means soft. The snow arrives like a gentle invasion. It then chases "small creatures" while "making small hearts soften," and whether that chase feels playful or threatening depends on who is being chased. The repeated "small" also shrinks the poem's viewpoint down to the scale of animals, or perhaps children, looking up.
The form helps create the effect of falling. There are six quatrains, and the first and last are the same refrain. The poem ends where it began, the way snowfall seems to carry on once you look away. The only change is "in the skies" becoming "in the sky." I can't tell whether that is deliberate, but the singular makes the ending feel slightly quieter and more settled.
The rhyme is loose. The first and last stanzas don't rhyme at all, and the four in between rhyme their second and fourth lines: "away" with "stay," "stars" with "shards," "cotton" with "soften," and "hair" with "air." Only two of these pairs are exact, and "stars" and "shards" are close but not quite matched, while "cotton" and "soften" share only a half-echo. The effect is of sounds that settle near each other without locking together, like flakes landing. Lines are short, mostly four to seven syllables, with no fixed meter, so the rhythm rises and drops unevenly.
The grammar adds to the movement. Line after line opens with an -ing word: Forming, Flowing, Enveloping, Refusing, Brightening, Plummeting, Chasing, Making, Falling, Soaking, Soaring. A participle has no end point, so the snow seems permanently mid-fall. Then the last stanza surprises us. Something described as "Falling" is also "Soaring through the air," and the verb lifts a descent into flight.
A few phrases are imperfect, and they are worth noticing rather than hiding. "Soaking up the light" sits awkwardly beside "Brightening the darkness," since snow usually throws light back rather than absorbing it, though the phrase can be read as flakes glowing as if full of light. Strictly speaking, a "follicle of hair" is the pocket in the skin that a hair grows from, so "strand" was probably meant. Even so, the phrase carries its intended meaning of weightlessness.
The poem's significance lies in how much it asks of one simple image. It is easy to follow, which makes it a good model of extended metaphor. It shows how a pile-up of comparisons can build a picture, and how single word choices like "infested" or "helpless" can complicate a scene that looks purely pretty. Nothing is offered about who wrote it or when, so the poem stands on its own words. On those words alone, it suggests that even the gentlest weather has an edge.