After a time Persephone became fond of Hades, he treated her as his most precious treasure. And everything was going well between them until Hermes, messenger of Zeus gave a message to the god of the underworld.
Finally Persephone returned to her mother, but before returning Hades gave 6 pomegranate seeds to his fiancée and this tied her to the underworld, in short she had to be with Hades 6 months a year, one month for each seed she ate
From now on each year, Persephone spends half of the year with Demeter and the other half with Hades. When Persephone is with Hades, the seasons are cold, but when she is with Demeter, the seasons are warm and fertile.