Snow that falls from a cloud but evaporates or sublimates before reaching the ground is called virga.
Virga occurs when precipitation descends into a layer of air that is too dry for the snow to survive. Some ice changes directly into water vapour through sublimation, while melted precipitation may evaporate as rain. From the ground, virga often appears as streaks hanging beneath clouds.
The process can cool the air beneath the cloud because evaporation and sublimation absorb heat. This cooling may create strong downdrafts and gusty winds. In dry environments, virga is common beneath high or mid-level clouds and may be visible across large distances.
Virga should not be confused with ordinary snowfall that reaches the surface. It can also involve rain, but the term describes the visible precipitation shaft that evaporates before arriving at ground level. Aircraft and weather radar can help detect precipitation that is not reaching the surface.