Cool Facts About Lightning

• Lightning is a giant discharge of electricityaccompanied by a brilliant flash of light and a loud crack of thunder. The spark can reach over five miles (eight kilometers) in length, raise the temperature of the air by as much as 50,000 degrees Fahrenheit (27,700 degrees Celsius), and contain a hundred million electrical volts.

• Some scientists think that lightning may have played a part in the evolution of living organisms. The immense heat and other energy given off during a stroke has been found to convert elements into compounds that are found in organisms.

• Lightning detection systems in the United States monitor an average of 25 million strokes of lightning from clouds to ground during some 100,000 thunderstorms every year. It is estimated that Earth as a whole is struck by an average of more than a hundred lightning bolts every second.

• The odds of becoming a lightning victim in the U.S. in any one year is 1 in 700,000. The odds of being struck in your lifetime is 1 in 3,000.

• Lightning can kill people (3,696 deaths were recorded in the U.S. between 1959 and 2003) or cause cardiac arrest. Injuries range from severe burns and permanent brain damage to memory loss and personality change. About 10 percent of lightning-stroke victims are killed, and 70 percent suffer serious long-term effects. About 400 people survive lightning strokes in the U.S. each year.

• Lightning is not confined to thunderstorms. It’s been seen in volcanic eruptions,extremely intense forest fires, surface nuclear detonations, heavy snowstorms,and in large hurricanes.

• Ice in a cloud may be key in the development of lightning. Ice particles collide as they swirl around in a storm, causing a separation of electrical charges. Positively charged ice crystals rise to the top of the thunderstorm, and negatively charged ice particles and hailstones drop to the lower parts of the storm. Enormous charge differences develop.

A moving thunderstorm also gathers positively charged particles along the ground that travel with the storm. As the differences in charges continue to increase, positively charged particles rise up tall objects such as trees, houses, and telephone poles—and people.

• The negatively charged bottom part of the storm sends out an invisible charge toward the ground. When the charge gets close to the ground, it is attracted by all the positively charged objects, and a channel develops. The subsequent electrical transfer in the channel is lightning.

• If your hair stands up in a storm, it could be a bad sign that positive charges are rising through you, reaching toward the negatively charged part of the storm. That’s not a good sign! Your best bet is to get yourself immediately indoors.

• The rapid expansion of heated air causes the thunder. Since light travels faster than sound, the thunder is heard after the lightning. If you see lightning and hear thunder at the same time, that lightning is in your neighborhood. If you see successive strokes of lightning in the same place on the horizon then you are in line with the storm, and it may be moving toward you.

• Not all lightning forms in the negatively charged area low in the thunderstorm cloud. Some lightning originates in the top of the thunderstorm, the area carrying a large positive charge. Lightning from this area is called positive lightning.

Positive lightning is particularly dangerous, because it frequently strikes away from the rain core, either ahead or behind the thunderstorm. It can strike as far as 5 or 10 miles (8 or 16 kilometers) from the storm, in areas that most people do not consider to be a lightning-risk area.

• During a thunderstorm, each flash of cloud-to-ground lightning is a potential killer. The determining factor on whether a particular flash could be deadly depends on whether a person is in the path of the lightning discharge.

In addition to the visible flash that travels through the air, the current associated with the lightning discharge travels along the ground. Although some victims are struck directly by the main lightning stroke, many victims are struck as the current moves in and along the ground.

• If you can hear thunder, you are within 10 miles (16 kilometers) of a storm—and can be struck by lightning. Seek shelter and avoid situations in which you may be vulnerable.

• Use the 30-30 rule, when visibility is good and there is nothing obstructing your view of the thunderstorm. When you see lightning, count the time until you hear thunder. If that time is 30 seconds or less, the thunderstorm is within six miles (ten kilometers) of you and is dangerous. Seek shelter immediately.

The threat of lightning continues for a much longer period than most people realize. Wait at least 30 minutes after the last clap of thunder before leaving shelter. Don’t be fooled by sunshine or blue sky!

• Most lightning deaths and injuries in the United States occur during the summer months, when the combination of lightning and outdoor activities reaches a peak. People involved in activities such as boating, swimming, fishing, bicycling, golfing, jogging, walking, hiking, camping, or working outdoors all need to take the appropriate actions in a timely manner when thunderstorms approach.

• The Fourth of July is historically one of the most deadly times of the year for lightning in the U.S.. In summer, especially on a holiday, more people are outside, on the beach, golf course, mountains, or ball fields. Outdoor jobs such as construction and agriculture, and outdoor chores such as lawn mowing or house painting are at their peak, putting people involved in danger.