Analysis
Formal Analysis
We can see that there are four stanzas: two quatrains and two tercets. Each verse has ten syllables, so we conclude that it is a Petrarchan sonnet with the following full-rhyme:
ABBA-ABBA-CDE-CDE
Interpretation
The poet suggests that there is a connection in nature (winter-summer). He thinks that we can find poetry in nature. He feels that nature transmit him poetry, but it is necessary to have a “romantic soul” to feel nature. In few words, Keats is talking about harmony : his soul is connected with nature, and this never ends.
Nature is seen as something cosmic, and because of this I can say that he is pointing out to the sublime.
We can see that in Romanticism the connection and harmony was based on soul.
Nowadays I think that it is quite difficult to feel connected with nature. What do you think?

As impressionist painters, this kind of literature, based on the feelings of a visual representation, try to move our soul into a certain emotion. Monet, Manet, Degas, Pisarro, used gardens and nature as a living character. Of course, the implied also the harmony, the balance, the sublime. Art is unique, in this hole thing of touching our soul.
Great post!