For decades, MayDay paradesinMoscow have taken placeunderclearblue skies, aircrafthaving deposited dry ice, silver iodideandcementpowdertodisperseclouds.
These offices, set up over the past 15 years, deploy artillery, rocket-launchers and aeroplanes to seed clouds with chemicals (usually silveriodide) that encourage droplets to form and fall where needed, or prevent the formation of destructive hailstones.