: As lightning passes through the atmosphere, it heats the air instantly, causing it to expand explosively. This rapid expansion creates a sonic shockwave that we hear as thunder.

: Lightning occurs when a large imbalance of electrical charges builds up within a cloud or between a cloud and the ground. This results in a giant electrical arc.

: Because light travels faster than sound, you can estimate a storm's distance by counting the seconds between the flash and the rumble. Every 5 seconds equals approximately 1 mile (or 3 seconds for 1 kilometer). Lightning Rules - National Weather Service