Rain falls early on a grey morning, and while most people find the day gloomy, the speaker is the exception. She loves the soft, noiseless drizzle, the swaying trees, and the wind. Even her umbrella is useless against the spray, and she doesn't seem to mind. The world turns into a misty blur of green and blue, and she is happy to get lost in it.
But the mood shifts in the last two stanzas. The rain stirs up a wish she can't explain, something deep inside her that she "knows not at all." Even when the rain waters the forget-me-not, a flower that suggests memory and remembering, she feels restless and burning, longing for "I know not what." The poem begins as a celebration of a rainy day and ends in quiet ache. The mood is dreamy, soft, and a little melancholy, as if the weather has opened a door to a feeling the speaker can sense but never quite name.