A long time ago Demeter lived happily with her daughter, Percefini.
Perecefini wandered off and Zeus captured her to make her his queen.
Hades made percefini eat seeds, and she ate 6, and the amount of seeds you eat is the amounts of months she cant leave the underworld. So Dementer made an agreement with Hades, after 6 Dementer can have her but after 6 mounths hades gets her back.
But while Percefini is there it becomes spring and winter.
For the 6 months while Percefini is away it becomes fall and winter.