Lightning is over 40,000 degrees Fahrenheit, so a bolt of lightning heats the air along its path causing it to expand rapidly.
Thunder is the sound caused by the rapidly expanding gases.
Seeing lightning and hearing thunder give you clues to how far away you are from a storm. Make it happen 1. After you see a flash of lightning, count the number of seconds until you hear the thunder. For every 5 seconds the storm is one mile away. Divide the number of seconds you count by 5 to get the number of miles.