How does it become possible to cause artificial rain by spraying silver iodide on the clouds?

Clouds are colloidal in nature and carry charge. For rainfall to occur, two oppositely charged clouds must combine. Silver iodide AgI being an electrolyte, helps in coagulation process between colloidal particles of water in cloud. Thus it forms bigger raindrops causing artificial rain. AgI is usually sprayed from aeroplane or remote controlled rockets.