The chemicals for that are known, tested, and approved to be harmless. They simply make water vapor form ice crystals, then clouds, then cause rain or snow as a result. You might have something if you can prove someone is using some unapproved chemical for some other purpose. Cloud seeding goes back over half-a-century in use.
Now, this might qualify...
On 10 November 1948, the US Navy did a test with an obsolete SB2C Helldiver dive bomber over Chesapeake Bay to test a possible radar jamming method using iron pentacarbonyl called X1. The plane flew at 500 feet over the bay while radar tracked it. The crew then released the 60 gallons of X1 in a spray behind the plane. The iron pentacarbonyl on contact with the moisture in the air burst into flame a few feet behind the plane, then turned into a black trail of smoke that slowly turned blood red then orange. The pilot and crew, alarmed, stopped the spray but not before most of the tank was emptied.
The cloud drifted and broke up, but not without additional issues. For days afterwards, civilians and local newspapers told stories of paint on cars and buildings peeling and holes appearing in it, clothing hung out to dry--particularly women's rayon hose--bursting into flames and disappearing. There were calls to the Pentagon and local military officials who told those concerned that there was nothing a plane could drop that would cause these things to happen...
The engineers involved were told to STFU and not do another test, at least for a good while...
Maryland's head toxicologist, not knowing about the test, attributed it to rotting vegetation that had produced Sulphur dioxide that combined with moisture in the air to create sulphuric acid...