Yip they sure can... Have a read of this...

Cloud Seeding Methods

The Beijing Weather Modification Office spent a lot of time researching how to prevent rain in the city during the Aug. 8 opening ceremony of the 2008 Summer Olympics. The government even guaranteed clear skies for the event -- a promise it managed to deliver on. The feat only took the launch of 1,104 rain dispersal rockets from 21 sites in the city to pull off

Even in areas with very low humidity, there's at least some water in the sky and clouds. A rainstorm happens after moisture collects around naturally occurring particles in the air, causing the air to reach a level of saturation at which point it can no longer hold in that moisture. Cloud seeding essentially helps that process along, providing additional "nuclei" around which water condenses. These nuclei can be salts, calcium chloride, dry ice or silver iodide, which the Chinese use. Silver iodide is effective because its form is similar to ice crystals. Calcium chloride is often used in warm or tropical areas.


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Northern China, where Beijing is located, doesn't receive much rain -- its rainfall levels are 35 percent below the world average, and some of its water supplies are significantly polluted. The area relies heavily on cloud seeding. Zhiang Qiang, who runs the Beijing Weather Modification Office, told the Asia Times that water levels in Beijing's water basins have increased up to 13 percent due to cloud seeding [source: Aiyar]. Cloud seeding also has been used to cool Beijing on hot days.