A cumulus cloud is formed when warm moist air from the surface rises and is lifted to higher altitude and condenses. It grows laterally and vertically into a large dense cloud called cumulonimbus, with strong turbulence within the cloud and strong outflow below the base of the cloud. The mature thunder cloud often has a cellular structure with diameter that can reach 3 to 5 kilometers and its top exceeding 10 kilometers. Thunderstorm cells may occur singly, in clusters, or in lines. Thunderstorms last an average of 15 to 30 minutes but may last much longer in some storms.
Thunderstorms are capable of producing hail, heavy rain, frequent lightning and strong gusty winds.
Some of the most severe weather occurs when a cluster of thunderstorms affect an area for a prolonged period of time. Downburst Downburst is a term used to describe a small area of rapidly descending air beneath a thunderstorm. The strong winds can reach very high speeds causing significant damage along its path and is extremely dangerous to aviation. The action of rising and descending air within a thunderstorm cloud separates positive and negative charges. Lightning is the discharge produced when differences between ground and atmospheric electrical charges are large enough to overcome the insulating effect of the air.