The speaker looks out at a stormy day, with a thin ivory light barely showing through heavy gray clouds. That weather quickly turns into a memory of someone else: a person whose eyes were sky blue when they were happy, clear and full of sun. The speaker also compares this person to the wind and to the clean, open feeling after a storm, so they seem to be both a restless force and a source of calm.
The middle of the poem is the most honest part. Being with this person was sometimes desperate, the speaker admits, but above all she felt "seen." That word matters, because it suggests what she misses most is being understood. The ending is quiet and blunt. Without the person there, the day is simply gray. The mood is wistful and a little bruised, with the sadness coming from the plain, small final line rather than from big declarations.