The temperature of the air in the lightning channel may reach as high as 50,000 degrees Fahrenheit, 5 times hotter than the surface of the sun. Immediately after the flash, the air cools and contracts quickly. This rapid expansion and contraction creates the sound wave that we hear as thunder.

With nearby lightning strikes the thunder will sound like a loud bang, crack or snap and its duration will be very short. As the shock wave propagates away from the strike center, it stretches, diminishes, and becomes elongated. Then other shock waves from more distance locations arrive at the listener.

Thunder is the sound caused by lightning. Depending upon the distance from and nature of the lightning, it can range from a long, low rumble to a sudden, loud crack. The sudden increase in temperature and hence pressure caused by the lightning produces rapid expansion of the air in the path of a lightning bolt.

In nature, a lightning flash and the associated thunder occur at almost the same time in a thunderstorm. A person on the ground sees the lightning flash before hearing the thunder because light at a speed of around 300,000,000 meters per second travels much faster than sound which moves at 340 meters per second.