What is lightning and thunder?

The diameter of a stroke of lightning is only a few centimeters, but its light intensity corresponds to that of one million 100 Watt glow lamps per meter.

The temperature of lightning is up to 30,000 degrees centigrade. The sudden increase in temperature makes the air expand explosively. This expansion of the air is what we hear as a thunderclap.

The electric current of lightning can reach several thousands amperes and the tension may go into millions of volt.

The process itself takes place within a couple  of hundred millionth seconds. Hence the energy of the lightning that flashes to the ground is limited, even if the effect is significant.

Most strokes of lightning carry a negatively charged electric current from the cloud to the earth. What we cannot see with the naked eye is the "forerunner", the so-called step leader, which is an electrically charged duct that builds from the cloud to the ground in a split second before the actual lightning.

Streamers build from the ground, or objects on the ground, reaching towards the cloud thereby contributing to forming the conductive path which will eventually determine the exact spot where the lightning will strike.

When lightning strikes, the duct is emptied of its charge from the ground towards the cloud making it look like the lightning strikes upwards.

Lightning is the result of electric charges being stored in thunderclouds. It requires special weather conditions where a certain volume of air packed with droplets of water is moved upwards.

In the process it cools down sufficiently rapidly to free a lot of energy (heat), which in turn condenses and intensifies the upthrust of the cloud. In other words, in this case the sun is the only actual source of energy.