Cloud Formation by Convection
On a hot sunny day, the sun heats up the surface of the land unevenly. Bare stony ground heats quickly while forests, lakes and shaded hillsides stay cool. The heated ground warms the air, which rises, creating thermals – wind that blows upwards. Birds love these and you often see them circling round and round as they hitch a free ride in the rising air currents. As the air rises, it cools below dew point and puffy cumulus clouds form, tending to grow to cumulus congestus or even mighty cumulonimbus thunderheads during the heat of the afternoon. This process is called convection.