Summarize how Greek Mythology explained the seasons. What is the story behind it?

Of the many explanations of natural phenomena, the Greek
myth  of Demeter and Persephone goes very far in explaining the seasonal change. 
Demeter, goddess of the hearth and home, was devoted to her daughter, Persephone.  One
day, when Persephone was picking flowers in a meadow, she plucked the Narcissus flower. 
After picking this particular flower of the underworld, a chasm opened and Hades, god of
the underworld who coveted the girl for his bride, appeared and kidnapped the young
goddess and took her to the underworld.  Demeter mourned the loss of her daughter and
wandered the earth, during which time no crops grew, and famine befell everyone.  Zeus,
the king of the Gods, understood that he was in a no-win position, as offending Hades
was out of the question and Demeter's disrespect was causing mounting trouble for his
devotees.  Zeus decreed that Hades must surrender his bride, unless she agreed to the
abduction.  When Hades gave her the fateful pomegranate, it "was adequate to ensure that
henceforth Persephone divided her time equally between her husband and her mother."  The
six months of the year when there is good weather, Persephone is with her mother
Demeter.  This is the time when the harvest grows and the sun is in full light.  When
Persephone is with her husband, the earth is cold and barren, indicating the time in
which mother awaits for daughter.