A long lightning flash at some distance from the observer produces the thunder we hear as a rumble.

Question

Quizplus · Accepted Answer

When lightning strikes, it heats up the air around it to thousands of degrees Celsius almost instantly. This causes the air to rapidly expand, creating a shock wave that we hear as thunder. If the lightning is far away, the sound waves from the shock wave will have to travel a greater distance to reach our ears, which can cause the thunder to sound like a rumble.

A Long Lightning Flash at Some Distance from the Observer