It is done under the umbrella of cloud seeding as the sibling comment said. And it is completely unregulated. You can actually go hire this company to cloudseed wherever you wish. You don't have to own the land, the people below don't get to give informed consent.

It was Yosemite.

I can think of two endgames. These cloud seeding agents have a dessicant effect on the forests. Leading to more forest fires under the guise of trying to prevent them.

Another longer term endgame I could imagine is to combine a solar minimum with ongoing established patterns of cloudseeding to create issues.