Types of Lightning

After you read about the different types of lighning on this page, try the Lightning Quiz to see how much you learned.

Cloud-to-Ground
Cloud-to-ground lightning is the most damaging and
dangerous form of lightning. It is not the most common type, but it is the one that is best understood. Most cloud-to-ground lightning strikes come from the negatively charged bottom of the cloud traveling to the positively charged ground below. Some cloud-to-ground lightning strikes deliver positive charges to the ground. Positive strikes are less common and come from the higher regions of the thundercloud.

Often, cloud-to-ground lightning bolts strike the highest object, like the top of a building or the top of a tall tree. The lightning strikes can cause fire and property damage. If a person is the highest object in the lightning bolt's path, the lightning may strike the person. Lightning strikes can cause severe injury or death. Cloud-to-ground lightning is the best understood type of lightning because it leaves so much evidence behind.

IntraCloud
Intracloud lightning is the most common type of lightning. This occurs between oppositely charged centers within the same cloud. This means that there are both positive and negative charges within the same cloud. Usually the process takes place within the cloud and looks like a bright flash of light which flickers. This bright flash may leave the cloud and the flash can be visible for many miles.

InterCloud
A less common lightning strike occurs between oppositely charged areas of different clouds. This means that there are positive and negative charges within different clouds and the strike travels in the air between them. This type of lightning is known as intercloud lightning.

Forms of Lightning

When lightning appears it can take many different forms and look very different. Some of these forms are described below.

Forked lightning appears as jagged or crooked lines of light. They can have several branches. Forked lightning can be seen shooting from the clouds to the ground, from one cloud to another cloud, or from a cloud out into the air. This lightning can strike up to 10 miles away from a thunderstorm and appear to be coming out of a clear blue sky. The phrase, "out of nowhere" or "out of the clear blue" might well describe some of these forked lightning strokes.

Sheet lightning appears as flashes of light that seems to light up or illuminate entire clouds. This makes the clouds visible far away.

Heat lightning is the term used to describe lightning flashes that are too far away from you to hear the thunder. Heat lightning is created by thunderstorms that are usually more than 10 miles away. The reason it is called heat lightning is that it appears most often in the hot summer when the sky overhead is clear.

Ball lightning is very rare. (In fact some scientists say it does not exist at all.) Reports of ball lightning have been made by passengers on planes and ships as well as from people that experienced it in their homes. These form of lightning appears as a glowing ball less than three feet wide. It lasts from a few seconds to several minutes and then disappears. Usually there is no damage from ball lightning except for burn marks left where it traveled through screens or windows.

St. Elmo's Fire appears as a blue or greenish glow above pointed objects on the ground. It was named for the patron saint of sailors. It is created when tiny positively charged sparks reach up in response to negative charges in the air or clouds above the ground. Instead of a lightning strike the glow appears from objects such as a ship's mast, a power pole, tall antennae, or the wings of an aircraft. If a thunderstorm is nearby, St. Elmo's Fire might be seen right before a lightning strike.

High-altitude lightning has been given other names such as "red sprites," "green elves," and "blue jets." This form of lightning appears as brightly colored flashes, high above thunderstorms. These flashes shoot up above the thunderstorm about the same time as other lightning discharges inside the storm cloud.

More about High-altitude lightning can be found at the Red Sprites and Blue Jets page or at the New Mexico Tech's Sprite Page.

Click the picture above to see a diagram of positive and negative charges within a cloud and the type of lightning strikes.