What sort of change is witnessed in the surroundings when the cricket sings the song?

Directions: Read the following poem carefully and answer the given question:

On the Grasshopper and the Cricket
                                 By John Keats
The poetry of earth is never dead:
When all the birds are faint with the hot sun,
And hide in cooling trees, a voice will run
From hedge to hedge about the new-mown mead;
That is the Grasshopper's -- he takes the lead
In summer luxury, he has never done
With his delights; for when tired out with fun
He rests at ease beneath some pleasant weed.
The poetry of earth is ceasing never:
On a lone winter evening, when the frost
Has wrought silence, from the stove there shrills
The Cricket's song, in warmth increasing ever,
And seems to one in drowsiness half lost,
The Grasshopper's among some grassy hills.