The seasons were explained in my favorite myth, that of Hades' love for Persephone, daughter of Demeter. Hades tricked her into the underworld, and Demeter was so distraught over her loss, she neglected her duties as a Goddess of Nature and fertility. As a result the plants did not grow, and crops failed. Persephone did not eat while in the underworld save 6 pomegrante seeds. As a result she had to return to the underworld for six months every year. During this time Demeter would mourn Persephone's absence and neglect the crops and thus we had winter, the period Persephone was gone.

http://en.wikipedia.org/wiki/Demeter...and_Persephone

Now, in a flat earth cosmology, I like the ideas of myths and gods being a 'real' force and not merely 'faces/figure heads' to explain a real world occurance.
1. I learn that legend on a D&D campaign, in wich we were epic pc's and we talked with the gods on a full greek world. (Well, but with dragons XD)

2. Yeha, you maybe are right, i just wanna have some fisic explanations too, so if the Sun God decides to travel closer to the Fire plane, know at least at a degree, how the climate is gonna be affected.

XD