Mechanism to trigger rain.
During cloud formation water can become supercooled, that is, it can get below freezing point but remain not frozen. This stage is so unstable that we can add some catalyst molecules to trigger rain. Historically humans used silver iodide, frozen carbon dioxide and some salts to trigger rain. This is known as cloud seeding.
Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practised in airports, where harsh weather conditions are experienced.
Wikipedia, Cloud Seeding, 2018
However nature uses different material to seed the clouds. Nature uses both sea salt and land dust to trigger rain. Wind at the surface of the seas causes waves to roll. Those waves release aerosols into the air carrying the sea salt. The wind carries both the sea salt and the land dust to the clouds. The sea salt and land dust cause the supercooled water to coalesce and trigger precipitation.
However 1400 years before it was discovered this was portrayed in the Quran:
[Quran 15:22] And We sent the seeding winds, then cause the rain to descend from the sky, and gave you water to drink, though you are not the guardians of its stores.