I found this in Wikipedia:
“Thailand started a rain-making project in the late-1950s, known today as the
Royal Rainmaking Project. Its first efforts scattered sea salt in the air to catch the humidity and dry ice to condense the humidity to form clouds.
[52] The project took about ten years of experiments and refinement. The first field operations began in 1969 above
Khao Yai National Park. Since then the Thai government claims that rainmaking has been successfully applied throughout Thailand and neighboring countries.
[53]On 12 October 2005 the
European Patent Officegranted to King
Bhumibol Adulyadej the patent EP 1 491 088 Weather modification by royal rainmaking technology.
[54]”
Cloud seeding - Wikipedia
I imagine Elon probably has knowledge of this and/or knows/employs people who do.