However , Jeff Tilley , director of weather modification at the Desert Research Institute in Reno , claimed in 2016 that new technology and research has produced reliable results that make cloud seeding a dependable and affordable water supply practice for many regions . Moreover , in 1998 the American Meteorological Society held that " precipitation from supercooled orographic clouds ( clouds that develop over mountains ) has been seasonally increased by about 10 % . " Despite the mixed scientific results , cloud seeding was attempted during the 2008 Summer Olympics in Beijing to coax rain showers out of clouds before they reached the Olympic city in order to prevent rain during the opening and closing ceremonies . Whether this attempt was successful is a matter of dispute , with Roelof Bruintjes , who leads the National Center for Atmospheric Research 's weather-modification group , remarking that " we can not make clouds or chase clouds away . " With an NFPA 704 health hazard rating of 2 , silver iodide can cause temporary incapacitation or possible residual injury to humans and other mammals with intense or chronic exposure . However , there have been several detailed ecological studies that showed negligible environmental and health impacts . The toxicity of silver and silver compounds ( from silver iodide ) was shown to be of low order in some studies . These findings likely result from the minute amounts of silver generated by cloud seeding , which are about one percent of industry emissions into the atmosphere in many parts of the world , or individual exposure from tooth fillings
opening
2008 Summer Olympics opening ceremony
Cloud seeding