San Francisco startup Rainmaker conducted an undisclosed cloud-seeding experiment over Homer, Alaska on August 23, dispersing silver iodide from drones to trigger rainfall. The company claims it produced 19 million US gallons of water in three hours without notifying residents beforehand.
Cloud seeding, a weather modification technique over 80 years old, works by dispersing compounds like silver iodide into clouds to form ice crystals that eventually fall as rain or snow. The process accelerates natural water vapor condensation. Rainmaker's drones are fitted with silver iodide flares that atomize water particles small enough to remain suspended in freezing clouds for hours before crystallizing into precipitation.
The technology requires ideal climate conditions such as mountainous or cold regions and depends entirely on existing cloud cover. Rainmaker's 19 million gallon output equates to roughly 0.01 inch of rain across 100 square miles.
Cooper Freeman, Alaska director of the Center for Biological Diversity, raised two objections. He criticized the lack of public notice to residents and questioned the safety of released silver iodide, noting no downstream environmental monitoring occurred. Freeman also argued cloud seeding does not address fundamental water conservation issues.
Rainmaker CEO Augustus Doricko defended the safety profile, stating the company releases 20 grams of silver iodide per flight distributed across thousands of square kilometers, resulting in ground-level concentration "in the parts per quadrillion, way below the threshold laid out by the FDA."
More than 50 countries are developing weather modification programs as global freshwater depletion accelerates. United Nations Secretary-General António Guterres said in July that the world is consuming freshwater faster than it can be replenished.
Jon Meyer, assistant state climatologist with the Utah Climate Center, noted that under ideal conditions cloud seeding produces only 5 to 10 percent additional precipitation. A 2017 study provided the first robust evidence that silver iodide functions as expected.
Alternative seeding agents are emerging. Recast Systems in San Francisco is testing a protein derived from soil amino acids that the company claims is safer, biodegradable and more efficient than silver iodide. Rainmaker currently operates in Idaho, Utah, Colorado and parts of the Middle East including Jordan.