Thunder happens because lightning rapidly heats the air around it, causing the air to expand explosively and create a shockwave. This shockwave is what we hear as the loud clap or rumble of thunder. The extremely hot air expands faster than the speed of sound, compressing the surrounding air and creating the thunder sound waves.

How Thunder Relates to Lightning

• Lightning is a massive electrical discharge caused by charge differences in clouds or between clouds and the ground.
• As lightning flashes, it heats the air to around 30,000 °C (54,000 °F), which is hotter than the surface of the Sun.
• The intense heat causes the air to expand quickly, generating a shock wave that produces thunder.

Why Thunder Rumbles and Rolls

• The thunder sound is actually the noise of the shockwave and air vibrations following the lightning strike.
• It can sound like a sharp crack or a long rumble depending on the lightning distance and atmospheric conditions.
• Because light travels faster than sound, we see lightning before we hear thunder, allowing us to estimate the distance of a storm.

In summary, thunder is the sound caused by the rapid expansion and explosive movement of air heated by lightning.