Thunder - online puzzles

Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, it can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave, similar to a sonic boom, often referred to as a "thunderclap" or "peal of thunder".