Vassavalāhaka sutta: Gods of the Rainy Thunderclouds

At Sāvatthī.

Seated to one side, that mendicant said to the Buddha:

“Sir, what is the cause, what is the reason why sometimes the heavens rain?”

“Mendicant, there are what are called gods of the rainy thunderclouds. Sometimes they think: ‘Why don’t we revel in our own kind of enjoyment?’ Then, in accordance with their wish, the heavens rain down. This is the cause, this is the reason why sometimes the heavens rain.”

The Linked Discourses on gods of the clouds are complete.