​​How do Thunderstorms form?

On a hot summer day the surface of the Earth is heated by the sun. The Earth's surface heats the air just above the surface through the process of conduction.
The action of warm air rising and cold air sinking (convection) plays a key role in the formation of severe thunderstorms. If the warm surface air is forced to rise, it will continue to rise, because it is less dense than the surrounding air. In addition, it will transfer heat from the land surface to upper levels of the atmosphere through the process of convection.
Two of the most important ingredients for thunderstorm formation are instability (unstable air) and moisture.