What causes the sound of thunder?

Thunder is caused by the rapid expansion and contraction of air surrounding a lightning bolt. When lightning heats the air to temperatures as high as 30,000 Kelvin, the air expands explosively, creating a shock wave. As the air cools and contracts, it generates the rumbling sound we hear as thunder. The delay between lightning and thunder occurs because light travels faster than sound. The intensity and duration of thunder depend on the lightning’s energy and the surrounding atmospheric conditions.