where we hope you learn about the fascinating weather that affects us day to day. This is a great learning resource for parents and teachers.


What is lightning?

Lightning is a very bright flash of electricity that happens in a thunderstorm.

  • The flash is actually a spark that crosses the gap between two clouds or between a cloud and the earth. 
  • The spark is caused by a negative charge of electricity in the clouds meeting a positive charge of electricity in the falling raindrops. 
  • The lightning flashes down a zig-zag path to the earth and can be seen as what we call forked lightning, as in the photograph above.
  • When a lightning flash is near the horizon, we cannot see the path of the lightning. Instead we see the sky about the horizon being lit.  This is called sheet lightning. 

The speed of lightning

We use lightning as an example of something very fast in phrases such as:

  • as quick as lightning
  • with the speed of lightning
  • as quick as a flash

How fast is lightning?

Lightning can travel at a speed of up to 136,000 miles an hour!

How do we know how close the lightning is?

When the electricity in a thunderstorm causes a flash of lightning, it causes a clap of thunder at the same time.

We see the lightning before we hear the thunder because light travels faster than sound.  Sound only travels at a speed of 12 miles in one minute.

It is easy to calculate how far away the lightning is by counting the seconds between the flash of lightning and the clap of thunder.  Calculate this at the rate of one mile for every 5 seconds.

If you count 10 seconds between the lightning and the thunder, the lightning was two miles away.

Lightning can strike as much as ten miles away from the centre of a storm.

How dangerous is lightning?

Lightning carries an enormous charge of electricity. Most of the flashes in a thunderstorm pass from one cloud to another and do no damage. If the lightning passes downwards to the earth and hits an object on the ground, it passes this charge of electricity into that object. Trees are burnt by lightning, metal can be melted and people can be killed. More people are killed in the world by lightning than by tornadoes.

Lightning can reach a temperature of 30,000  °Celsius, which is hotter than the surface of the Sun.

How can I be safe from lightning?

  • Do not use the phone since telephone lines conduct electricity.
  • Do not touch metal taps as metal conducts electricity.
  • Do not go fishing or boating during a thunderstorm.
  • Do not play golf during a thunderstorm. Many golfers have been hit by lightning because of their metal clubs.
  • If you are outside, stay away from water; water conducts electricity.
  • If you are outside, stay away from trees or electricity poles.
  • If your hair stands on end (which is caused by electricity in the air) crouch down close to the ground with your hands on your knees and your head tucked between them.

Lightning Safety - National Weather Service information

Volcanic Lightning

When people talk about lightning, they are usually talking about the lightning that we see during a thunderstorm.  Volcanoes can also produce lightning when they erupt.

Scientists do not fully understand this.  They believe that the particles of volcanic ash carry an electric charge.

Here is a photograph of lightning above the Japanese volcano Sakurajima as it erupts.