text: how does lightning cause thunder? i know that they lightning is faster than the thunder... and why... and i know that the lightning causes thunder but how does the lightning cause the thunder plus who had a t-storm today?! thunder is the sound of the shockwave caused when lightning instantly heats the air around it to up to 30 000 °c (54 000 °f). that super-heated air expands rapidly, then contracts as it cools. the rapid expansion/contraction generates sound waves, making the sound that is called "thunder."