The context of the poem is the historical moment of the civil rights struggle that in the 1950s decided to commence direct actions to end segregation and earn equal rights for African Americans. The raisin in the sun is a symbol for African Americans who could not realize their fullest potential and follow their dreams due to the denial of their civil rights that should guarantee their access to proper education, health care and employment.
Hughes was the main leader of the Harlem Renaissance and as an artist and a social activist he was dismayed to see so much potential in his community wasted due to racial discrimination and segregation. The image of a raisin in the sun is that of potential. If watered and cared for the raisin can become a delicious fruit or be turned into excellent wine. However, if it is just left there, it dries up and rots. Hughes was warning society that such outcome might be explosive.