Bananas ripe and green, and ginger-root,
Cocoa in pods and alligator pears,
And tangerines and mangoes and grape fruit,
Fit for the highest prize at parish fairs.
Set in the window, bringing memories
Of fruit-trees laden by low-singing rills,
And dewy dawns, and mystical blue skies
In benediction over nun-like hills.
My eyes grew dim, and I could no more gaze;
A wave of longing through my body swept,
And, hungry for the old, familiar ways,
I turned aside and bowed my head and wept.
Fond memories of the past turn to sadness in the present. Elsewhere McKay  voiced his concerns  with America and contrasted it starkly with his homeland. 
 Notice how the “wave” of longing itself recalls the tropical climate he’s evoking. 

Tropics in New York