Rainmaking

Rainmaking, method by which cloud precipitation is increased. Modern techniques of cloud seeding create conditions within clouds in which crystals, or water drops, become heavy and large enough to fall to earth as rain. Generators or airplanes inject the bottoms of clouds with substances called seeding agents—such as ammonium nitrate and urea, silver iodide crystals, or dry ice—to begin this crystalmaking process. Rainmaking can increase an area's water supply or reduce the intensity of an approach storm.