Haha this is just another school project. I'm probably going to put a few up here. But please read my Maximum Ride story: Wondrous World of Fang!
Long before the seasons changed, before Persephone was kidnapped by Hades, there was no such thing as precipitation. Flowers did not need rain; anyone blessed by the goddess Demeter could grow any amount of vegetation they needed.
Now, people had learned to wonder the seas, and they could walk on land. The dead went to the Underworld, but not the living. However, the one domain that had not been perpetrated by people was the sky. Humans are a curious bunch. No matter how much they know, they want to know more. Therefore, air travel had become the new curiosity of the humans.
Zeus is a very jealous god; he did not want his domain to become tainted with the human race. Zeus sent Medusa, a horrid monster, to petrify all the humans working on ways to fly.
Meanwhile, Perceus, Zeus' mortal son, had received a prophecy:
"Zeus' monster will petrify;
an order his son will defy.
Greatly angered, tries to burn,
gives the world quite a turn.
An endless cycle will become,
and help the mortals grow a ton."
Perceus had been given an order not to interfere with Medusa. However, just as the prophecy predicted, Perceus went on a quest to destroy Medusa. After successfully locating her, he proceeded to cut off her head.
Zeus was furious that his son disobeyed him and ordered his god son Apollo to burn the earth because of Perceus' interference. Apollo obeyed and drove his chariot close enough to the earth to cause fires to start burning houses and trees. Also, this intense amount of heat caused water to evaporate at great rates. Poseidon was anxious that his kingdom was disappearing because of Zeus' plan.
So, Poseidon sends water into the atmosphere to drive Apollo further up into the atmosphere. However, Poseidon is not always able to hold Apollo at bay high in the atmosphere. When Poseidon does not send enough water into the atmosphere, the sun is able to shine. When Poseidon has strength to send enough water into the atmosphere to hold Apollo back, it is cloudy and rainy. This rain allows Poseidon to get back the water that Apollo has taken and return it to the sea. Therefore, the water cycle continues to this day as an ongoing feud between Apollo and Poseidon, with Zeus' occasional contribution with lightening to attempt to force Poseidon out of the sky.