A Chinese weather experiment has somewhat backfired as highways are closed around Beijing due to the excessive snowfall that was induced by seeding clouds with chemicals. Yes, this is a common practice around the world. This was done in an attempt to generate more precipitation, and will likely become more frequent as Beijing fights an uphill battle with longstanding drought.

Some persist in the notion that this activity wont have any detrimental impact on the greater environment, by diverting weather systems, and contaminating the air and soils with toxins.

This article discusses the use of Silver Iodide in its capacity to alter the behavior of cloud systems.
http://www.technologyreview.com/infotech/20463/