why is thunder so loud

Thunder is so loud because it is the sound created by the rapid expansion of air heated by lightning. When a lightning bolt passes through the air, it heats the surrounding air to about 27,000°C (approximately 48,600°F) extremely quickly. This causes the air to expand explosively, compressing adjacent air and creating a shock wave similar to a sonic boom. This shock wave produces the loud booming noise we hear as thunder. The initial rapid expansion is followed by cooling and contraction, which creates complex sound waves that can travel many miles and vary in loudness and rumbling character depending on the lightning and atmospheric conditions. Additionally, atmospheric temperature layers called inversions can reflect and amplify the sound, making thunder seem even louder in some situations.