Aircraft can accidentally punch holes in clouds, leaving a trail of snow or rain in their wake. Turboprop and jet aircraft that climb or descend under certain atmospheric conditions can inadvertently trigger what's known as cloud seeding.
June 4, 2010: Earth and space are about to come into contact in a way that's new to human history. To make preparations, authorities in Washington DC are holding a meeting: The Space Weather Enterprise Forum at the National Press Club on June 8th.
A laser has been used to generate small clouds on demand in lab, and real-world experiments suggest this could be a way to call down rain when it's needed.