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LIGHTNING FAQs

What tends to happen when lightning strikes ground is that it fuses dirt and clays into silica or sand. The result is often a black, glassy rock (called a fulgarite) in the shape of a convoluted tube. The shape in the ground is the shape of the path the lightning current followed in the ground. There is often damage to grasses along this path too. Lightning traveling down a tree trunk turns water to steam. If it gets under the bark into the surface moisture of the wood, the rapidly expanding steam can blast pieces of bark from the tree, and the wood along the path is often killed.
Positive lightning is often considered more dangerous because its electrical field is stronger (forming at the top of the storm), the flash duration is typically longer, and its peak charge can be much greater than a negative strike. Plus, positively charged lightning can occur near the edge of a cloud or strike more than 10 miles away – when people aren't aware of the danger.
According to the National Weather Service, during the past 30 years (1979-2008) lightning killed an average of 58 people each year. Documented injuries average about 300 per year.
Lightning can have 100 million to 1 billion volts, and contains billions of watts.

Damage and Impacts

Lightning losses

While it is difficult to quantify lightning losses, it is estimated that $4-5 billion damage occurs each year. Likewise, the cost of lightning protection to safeguard critical equipment and facilities from lightning strikes during severe weather is enormous.

According to the National Weather Service, during the past 30 years (1979-2008) lightning killed an average of 58 people each year. Documented injuries average about 300 per year, although undocumented injuries are likely to be much higher. Most casualties result from inappropriate behavior during thunderstorms, particularly when people are caught outdoors during recreation or organized sports. Being aware of - and following - proven lightning safety guidelines can greatly reduce the risk of injury or death.

What does lightning do to people?

This woman might not be laughing if she understood her risk of being struck by lightning was incredibly high. Her "electrified" hair should have been a dead giveaway that lightning from a nearby mountain thunderstorm put her life in extreme danger.

Cloud-to-ground lightning can kill and injure people by direct or indirect means. It is not known if all people are killed who are directly struck by the flash itself. The lightning current can branch off to a person from a tree, fence, pole, or other tall object. In addition, flashes may conduct their current through the ground to a person after the flash strikes a nearby tree, antenna, or other tall object. The current also may travel through power or telephone lines to a person who is in contact with electric appliances, tools, electronics, or a corded telephone. Lightning can also travel through plumbing pipes and water to a person in contact either with a plumbing fixture or a person in water, including bathtubs, pools, and the running water of a shower.

Damage to the human body:
Lightning affects the many electrochemical systems in the body. People struck by lightning can suffer from nerve damage, memory loss, personality change, and emotional problems. There is a national support group for lightning and electric shock survivors.

An example is some single nerve cells, such as those extending from the brain to the foot, can be as long as 6 feet or more. These types of cells are most prone to lightning damage due to the instantaneous potential difference across the length of the cell as lightning begins to enter the body.

The intense heat of the lightning stroke can turn sweat instantly to steam and the tremendous pressure of the steam has been known to blow people's boots, shoes, and clothing off them. In places where metal is in contact with or close proximity to the body, such as jewelry or belt buckles, burn marks are found. Likewise, burn marks are found in places where the body had been sweaty, such as the feet, underarms, and chest.

How to stay safe when lightning is around - "If you can hear it, fear it!"

The best defense is plan ahead and avoid exposure to lightning when a thunderstorm occurs. Know where safe shelter is located and leave enough time to reach safe shelter before your danger level is high. Don't be an isolated tall object, and don't be connected to anything that may be an isolated tall object.

If you are outdoors when you hear thunder, stop your activities and seek safe shelter immediately! Once inside a safe building or vehicle, stay there for at least 30 minutes after you hear the last rumble of thunder.

HOW DOES NSSL CONTRIBUTE?

NSSL researchers are active in promoting lightning safety education. One reason for this is that lightning is a single-victim event, unlike flash flooding which can kill many people at one time. Since it is not possible to issue specific warnings for every lightning flash for each person, researchers feel compelled to provide tools to help people protect themselves from lightning danger.

NSSL's scientists and collaborators did a study to find out how close is "too close" for lightning. They found that 80% of the next lightning strikes in a storm are within 2 to 3 miles of each other in certain weather conditions in Florida, but more typically lightning strikes are about 6 miles from each other. Their research was incorporated into a paper on updated recommendations for lightning safety Offsite which set forth some simple concepts for lightning safety (2002).

Posters
Taking shelters under trees is dangerous - recent studies of lightning victims showed several highly-vulnerable situations and activities, but the one that stood out was taking shelter under trees. NSSL scientists developed posters on this threat, called "LIGHTNING DANGER! STAY AWAY FROM TREES DURING THUNDERSTORMS!" Over 16,000 copies have been printed in English and Spanish. The posters were distributed to teachers, NWS staff, and others.

Lightning policy for sports associations
NSSL scientists gave valuable input to the NCAA Committee on Competitive Safeguards and Medical Aspects of Sports as they developed guidelines for lightning safety at NCAA sporting events. They also helped create a position statement regarding lightning safety for athletics and recreation for the National Athletic Trainers' Association

Protecting WSR-88Ds from damage
NSSL worked with the NWS to carefully evaluate the performance on the WSR-88D lightning protection system and make recommendations for improvement. Part of the process included creating a 3-D computer simulation of a cloud-to-ground lightning stroke striking a radar antenna tower.

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