Why thunder occurs?

Thunder is caused by lightning. The charge transfer that occurs within the electrically charged storm clouds, between the storm clouds, or between the storm cloud and the ground creates lightning strikes. During the lightnings, the temperature of the air around the lightning line can reach 30,000 °C. This value is approximately five times the surface temperature of the Sun. However, this line formed by the ionized state at high temperature is quite narrow (1-4 cm) and effective on the microsecond scale. It has been determined that the width of the load transfer line can reach 10 cm in the measurements made by photographing the lightning strikes and 5 cm in the measurements based on the analysis of the changes in the crystal structure of the lightning striking rocks.

The pressure of the heated air can increase to 10-100 times the normal atmospheric pressure and the air expands suddenly. This causes shock waves to form in the air along the lightning line, as during sonic eruptions. The sounds similar to the explosion we hear during thunder are caused by this situation.

Thunder can be heard in the form of a sudden and violent cracking sound or louder and prolonged rumble, depending on the way lightning occurs and its location.

It is impossible for thunder to appear without lightning. However, storm clouds are not always required for lightning to occur. Lightning strikes can also be observed during volcanic eruptions and large forest fires.