Here's why:

* Light travels much faster than sound. Light travels at approximately 186,000 miles per second, while sound travels at roughly 767 miles per hour. This means you see the lightning almost instantaneously, but the sound of thunder takes time to reach you.

* Counting the seconds helps estimate distance. Sound travels at a relatively predictable speed. By counting the seconds between seeing the lightning and hearing the thunder, you can estimate how far away the storm is.

Here's a simple rule of thumb:

* Every 5 seconds between lightning and thunder means the storm is about 1 mile away.

So, the correct sequence is:

1. See the lightning.

2. Start counting seconds when you hear the thunder.

3. Multiply the number of seconds by 0.2 to get an approximate distance in miles.

Let me know if you'd like to try an example!