The question is Shelley’s and finds its answer in what has gone before in the Ode to the West Wind:
Who chariotest to their dark wintry bed
The wingèd seeds, where they lie cold and low,
Each like a corpse within its grave, until
Thine azure sister of the Spring shall blow
Her clarion o’er the dreaming earth …
Spring is here already, waiting for moment to blow her trumpet to announce birth and rising.
For me Winter arrived today when I saw my first redwing of the year, come over from Scandinavia to spend the winter eating berries. My one was on a hawthorn bush. The next movement across my handlebars was a lesser spotted woodpecker. Two good sightings to celebrate winter.