What is virga in meteorological terms?

Virga refers specifically to rain that falls from the atmosphere but evaporates before it can reach the ground. This phenomenon often occurs in arid or semi-arid regions where the air below the cloud base is very dry. When rain droplets descend from a cloud, they may evaporate completely due to the lower humidity levels, leading to a situation where it appears to rain without any actual precipitation reaching the earth.

The other options describe different meteorological concepts but do not align with the definition of virga. Dense cloud cover, for instance, refers to a thick layer of clouds that can block sunlight but does not specify the behavior of precipitation. Heavy snowfall and types of fog relate to solid precipitation and low visibility conditions, respectively, and do not pertain to the evaporation of rain in transit. Thus, identifying rain that vanishes before making it to the surface is the key characteristic that defines virga.