Thunderstorms form when warm moist air rises. The warm moist air rises in three ways….topography (mountains), a front or daytime heating. As the warm air rises it cools and condenses into a cloud. At this point the cloud would be called a cumulus cloud.
The cloud will grow if warm moist air continues to rise. The rising air is called an updraft. The updraft will continue to add water droplets to the cloud. The water droplets will continue to grow in size and weight. When the updraft can no longer keep the water droplets up, they fall as rain. As the rain falls it drags down air with it. At this point the cloud would be called a cumulonimbus cloud.
The stronger the updraft the higher the cumulonimbus cloud will rise. As the cumulonimbus cloud increases in height the temperature decreases. For every 1,000 feet in elevation, you go up, you roughly lose 4 degrees Fahrenheit. Eventually, the temperature will be below 32 degrees and the rain droplets will freeze, forming hail. The hail will continue to grow as it is caught in the cloud’s up and downdrafts. The ice pellets and water droplets hit each other causing an electrical charge, forming lightning. It is now considered a thunderstorm.