Answer:
The poem kicks off on a high note, with a tonality of vigour, energy and beauty. However, by the third line, the tonality of the poem shifts to one of solemness and ethereality with a tint of gloominess.
Notice words like
summer's day (Line 1)
lovely, temperate (Line 2)
And then in lines 3,4,5 we have words such as
rough winds, summer's lease....too short, too hot.
See also the in the 4th before the last line, the poet uses words such as death and wand'rest, thus giving it a 'cloudy' ending.
Cheers!
