Three factors are necessary to cause a thunderstorm:

• The atmospheric layers must have different temperatures
• The warmer atmospheric layer closest to the ground must contain humidity
• The atmospheric layers may not remain stable. The warmer lower atmospheric
  layer rises to the colder one above. This can be caused by wind or a change in
  air pressure but also by the topography.

The rising moist warm air cools down in the higher colder atmosphere. As a result of the condensation there is additional warmth which accelerates the buoyancy. The upwinds prevent rain drops or ice corns from falling to the ground; they are carried back up by the upwind. Not until they have become too heavy for the upwind do  they fall back to the ground. Depending on the temperature they turn into raindrops, ice pellets or even hail.

The high vertical air speed in connection with the ice crystals of varying charges lead to electric currents at the surfaces between the upwinds and the downwinds is discharged by lightening. This in turn makes the air expand suddenly which breaks the sound barrier. That is what causes thunder. Due to the fact, however, that lightening spreads at the speed of light and thunder only at the much slower speed of sound, it is easy to calculate one’s distance from the storm as a result of the  distance between the two events.
If you are in a building with a lightening rod or in a car made of metal you can feel safe during a thunderstorm and must not be afraid of being hit by lightening. If you are outside and are overtaken by a thunderstorm you should avoid all tall trees and buildings that are not protected by a lightening rod. One should never be the  highest point in a terrain. Lightening will always strike in the next highest tree or the highest building. That is why it is important to keep your distance from the  highest trees in a forest during a storm. If you are beneath a tree that is struck by lightening during a storm you can certainly be hurt or even killed. It is just as  important to get out of water during a thunderstorm. If the electricity or telephone is supplied via overhead lines, all electrical devices should not be on during a storm.
Nowadays what is even more important than lightening are the events that accompany the storm, such as squalls, floods due to strong rain and crop damage as a result of the hail. That is why it is so crucial to take precautions before the onset of the storm to prevent events such as these from taking place.

No one has yet been able to make use of the electrical energy which becomes available as a result of lightening.