Thunder is so loud because it is like an explosion.
It's a sound caused by lightning, which is like a giant spark of electricity in the sky. The lightning is incredibly hot, over 50,000 degrees! It very quickly heats up the air around it, and the air expands outward very fast The rapid changes in the air are what we hear as thunder.
Sound is our brain's way of interpreting vibrations. When someone speaks to you, their voice vibrates the air and you hear the vibrations as sound. The vibration caused by lightning are much more powerful than a person's voice. That's why you may want to block your ears! Lightning also usually branches out in many different directions in the sky. When we hear thunder, it's usually not just the rumbling of one part of the sky. It's the rumbling of a lot of different parts.
by Mya Kagan (Whyzz writer)
How Far Away Is Lightning?The light from lightning reaches our eyes faster than the sound of thunder reaches our ears. It travels much faster. Thunder shows up later, which is why a lot of people think that thunder and lightning are two separate events. After you see a flash of lightning, count the seconds until you hear thunder. If you count 5 seconds between lightning and thunder, it means that the lightning is about a mile away. It takes about 5 seconds for thunder to travel each mile. If you hear thunder 10 seconds after seeing lightning, how far away is it? Divide 10 by 5 to get your answer.