Thunder and Lightning

In the United States, lightning routinely kills more people each year than tornadoes and hurricanes COMBINED. Tornadoes, hail, and wind gusts get the most attention, but only lightning can strike outside the storm itself. Lightning is the first thunderstorm hazard to arrive and the last to leave.

Thunder is the sound wave resulting from the extreme heat generated by a lightning flash. (Lightning is five times hotter than the surface of the sun!) When lightning occurs, it heats the surrounding air to that same incredible temperature in a fraction of a second. The air expands so fast that it forms a shock wave similar to a sonic boom, or thunder.

One simple way to estimate how far away a thunderstorm is involves counting the number of seconds between a flash of lightning and the clap of thunder. Divide the number you get by 5 to estimate the distance to the lightning in miles. If the seconds get shorter the storm is getting closer and you should take cover!.

Here's another teaching applet you can use to explore the relationship between lightning and thunder. You can move the person around by 'dragging' with the mouse. If your computer has sound you'll hear the thunder but you can also see the sound wave and tell when the person hears the thunder. How many seconds does it take the sound to travel to where the person is?

Continue to learn about winter storms