This is fine sonnet and symbolic poem in which the grasshopper is a symbol of hot a summer and the cricket is of very cold winter.
Every poet has been attracted towards the beauty of nature and so has Keats been. He finds nature beautiful in all seasons not excluding the hot summer and cold winter. He says that the earth is always singing. When the birds stop singing in the hot summer finding cool place, we find the grasshopper singing and flying from hedge. He sings tirelessly and when tired, rests beneath some weed. When the birds are silent in very cold the earth never stops and expresses its pleasure through different beings like the cricket. It sings the beautiful songs from the stones. It seems to be increasing in warmth every moment and half-asleep human being feels it to be a grasshopper’s song coming from grassy hills.