[Drago]

Common and benign since 1968:

https://www.publicpower.org/periodical/article/smud-among-other-utilities-uses-cloud-seeding-increase-hydropower

https://www.kcra.com/article/aircraft-cloud-seeding-norcal-how-it-can-help/39441869

https://www.mtdemocrat.com/news/the_divide/smud-plans-to-double-its-cloud-seeding/article_3863aa46-263c-5225-8cfd-f7964fda6c28.html

[cgbg]

The question is how often is cloud seeding done?

It is relatively rare these days in most of the US.

Here is an article from 2021 suggesting it was limited to eight states during one drought period:

https://www.scientificamerican.com/article/eight-states-are-seeding-clouds-to-overcome-megadrought/

In addition chemtrails supposedly use aluminum which is not a chemical used in cloud seeding.