The Hawaiian legend of Pele and Kamapuaʻa explains why the east side of the Big Island is wet and the west side of the Big Island is dry. The story is as follows:
Why the Big Island has a wet and dry side: the Legend of Pele and Kamapuaʻa
Legend has it that two deities — the volcano goddess Pele and the demi-god Kamapuaʻa (the latter of whom could control the weather) — once were lovers. However, their first romantic encounter Pele grew scared and broke of their companionship:
‘Not again,’ she whispered. ‘Leave me alone. I came here to be queen. But you are more powerful than I. Stay away. Take the lush green valleys of Hilo, Hamakua, and Kohala. Keep them wet and fertile. I’ll stay here in Ka’u and Kona and balance your rain with the fire of the sun.’
This deal divided the island in two with Pele taking the hot and dry western half, and Kamapuaʻa the rainy east side.
You can read a longer version of this tale on the CoffeeTimes website.