How Does Cloud Seeding Work?

Raindrops and snowflakes need tiny particles called nuclei to form around. In cold clouds with supercooled water, silver iodide particles, whose crystal structure resembles ice, help ice crystals form; these grow and fall as snow or rain. In warm clouds, hygroscopic particles such as salt attract moisture and help droplets merge into larger drops. Aircraft, rockets or ground generators deliver the particles into suitable clouds. Cloud seeding cannot create clouds, and measuring how much extra rain it produces remains scientifically challenging.