Rain forms when supercooled water molecules condense around inert dust particles in high altitudes. Cloud seeding involves inserting silver iodine (fine inert dust) into clouds from planes or ground-based emitters and thus increasing the likelihood of raindrop formation.

Currently, cloud seeding is used in different parts of the world as an experimental way of controlling the weather. In the case of the 2008 summer Olympics, China used artillery shells to fire silver iodine into the clouds in conjunction to the traffic ban to ensure perfect blue skies over Beijing. Cloud seeding is also used in Tasmania in effort to refill dams and reservoirs on a statewide scale.