Lightning why it occurs

Cloud-to-ground lightning is divided into two different types of flashes depending on the charge in the cloud where the lightning originates. Thunder is the sound made by a flash of lightning.

As lightning passes through the air it heats the air quickly. This causes the air to expand rapidly and creates the sound wave we hear as thunder. Normally, you can hear thunder about 10 miles from a lightning strike. Since lightning can strike outward 10 miles from a thunderstorm, if you hear thunder, you are likely within striking distance from the storm. Learn More: Thunderstorm Development or return to Contents page.

The sound of thunder travels about a mile every 5 seconds. If you count the seconds between the flash of lightning and the crack of thunder and divided by 5, you get the number of miles away from you 10 seconds is 2 miles.

Please Contact Us. This electric current is known as the return stroke. We see it as the bright flash of a lightning bolt. Thunder and lightning occur at roughly the same time although you see the flash of lightning before you hear the thunder. This is because light travels much faster than sound. Lightning happens when the negative charges electrons in the bottom of the cloud are attracted to the positive charges protons in the ground.

The accumulation of electric charges has to be great enough to overcome the insulating properties of air. Thunder is caused by lightning.

The bright light of the lightning flash caused by the return stroke mentioned above represents a great deal of energy. The air that is now heated to such a high temperature had no time to expand, so it is now at a very high pressure. The high pressure air then expands outward into the surrounding air compressing it and causing a disturbance that propagates in all directions away from the stroke. The disturbance is a shock wave for the first 10 yards, after which it becomes an ordinary sound wave, or thunder.

Fun fact: thunder can seem like it goes on and on because each point along the channel produces a shock wave and sound wave, so what you hear as thunder is actually an accumulation of multiple sound waves from the different portions of the lightning channel.

Static means not moving. Static charges are always "looking" for the first opportunity to "escape," or discharge. Your contact with a metal doorknob—or car handle or anything that conducts electricity—presents that opportunity and the excess electrons jump at the chance. So, do thunderclouds have rubber shoes?

Not exactly, but there is a lot of shuffling going on inside the cloud. Lightning begins as static charges in a rain cloud. Winds inside the cloud are very turbulent.

Water droplets in the bottom part of the cloud are caught in the updrafts and lifted to great heights where the much colder atmosphere freezes them.

Meanwhile, downdrafts in the cloud push ice and hail down from the top of the cloud. Where the ice going down meets the water coming up, electrons are stripped off.