Who Parjanya is
Parjanya is the rain. More exactly he is the rain cloud, and the god who rides it. The Sanskrit word means both, and in many verses of the Rigveda it is hard to say which one the poet has in mind.
He is a small god by count. Only three hymns of the Rigveda are his, and his name appears fewer than thirty times. Even so, the best of the three (5.83) has rarely been bettered as a picture of the monsoon breaking.
The poets see him as a bull. He roars, and he lays seed in the plants. He drives a chariot heavy with water and whips his rain messengers forward like a charioteer whipping horses. When he fills the sky with cloud, the sound is like a lion roaring far away. The winds burst out and the lightning falls. Trees are split, and even innocent people run for cover. Then the plants shoot up, and there is food for everything that lives.
He carries a waterskin, and the poet asks him to open it, tip it downward and pour until the hollows and the high ground are level. A few verses later, with the land soaked, the same poet says politely that it is enough. You have rained, he says, and now please hold it back.
The hymns call him father. The earth is the mother he waters, and one verse says that the Father's flow moistens the Mother and that parent and child both live on it. The Atharvaveda puts it in a single line: Earth is my mother, Parjanya is my father. Another short hymn calls him the son of Dyaus, the sky, and says he puts the seed of life in cows, in mares, in the plants and in women.
Thunder and roar, and plant the seed. Fly round us in your chariot full of water.
He can be changeable. One hymn says he is barren at one time and fruitful at another, and takes whatever form he likes. Farmers have always known that about rain.