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.

Which comes first thunder or lightning Why?

The reason we see a flash of lightning before hearing thunder is because light travels faster than sound. The speed of light depends on what it is moving through - being slow in gases, fast in liquids, and even quicker in solids. In the air, sound travels at around 332 metres per second.

Why do we hear thunder a few seconds after lightning?

Lightning is a gigantic spark of electricity that connects the thundercloud to the ground. It's so hot that it causes the air to “explode” — that's the sound we hear as thunder. However, thunder travels much slower than the light from a lightning bolt, so we usually hear thunder a few seconds after we see lightning.