Lightning heats the air so that it expands explosively. The loud clap is thunder. Light waves travel so rapidly that lightning is seen instantly. Sound waves travel much more slowly, so a thunderclap may come many seconds after the lightning is spotted.

Thunderstorms kill approximately 200 people in the United States and injure about 550 Americans per year, mostly from lightning strikes. Have you heard the common misconception that lightning doesn’t strike the same place twice? In fact, lightning strikes the New York City’s Empire State Building about 100 times per year.

https://www.youtube.com/watch?v=XFq8Ome91_o