Virga

weather · desert · sky science

Rain that vanishes. A virga is precipitation that falls from clouds but completely evaporates or sublimates (turns straight from ice to air) before hitting the ground. It looks like rain or snow falling from the sky, but the droplets never make it down.

Ice falls first. High up in the sky where it is cold, precipitation starts as ice crystals. As the ice crystals fall lower where it is warmer, they melt into water droplets, then evaporate into invisible air before reaching the ground.

Desert specialty. Virga is super common in dry places like deserts and the western United States because the air is so dry that water droplets disappear before landing. It is also frequently seen across Australia, North Africa, and the Middle East.

Air pressure changes it. The reason virga happens so often is because of compressional heating. As air gets pushed down toward the ground, pressure increases and temperatures rise, which makes water droplets evaporate faster than they can fall.