Silver iodide can trigger artificial rain and snow through a process called cloud seeding.

Cloud seeding was first discovered in 1946 by Vincent Schaefer and Bernard Vonnegut at the General Electric Research Laboratory. They found that silver iodide is particularly effective because its hexagonal crystal lattice structure is nearly identical to that of natural ice. This similarity allows the chemical to act as a 'nucleating agent,' providing a surface for supercooled water droplets to bond and freeze at temperatures higher than they normally would.When silver iodide is released into a cloud via airplanes or ground-based generators, it initiates a chain reaction. The newly formed ice crystals grow rapidly by drawing moisture from surrounding water droplets in a process known as the Bergeron-Findeisen effect. As these crystals gain mass, gravity pulls them toward the earth. Depending on the air temperature near the ground, they arrive as either snow or rain.The scale of these operations is significant. According to the World Meteorological Organization, over 50 countries currently have weather modification programs. In the United States, states like Wyoming and California use cloud seeding to increase mountain snowpack by an estimated 5% to 15% annually. While effective for localized water management, the technique requires specific atmospheric conditions, such as existing clouds with sufficient moisture, to work successfully.