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Home > Lightning: Questions and Answers

Lightning: Questions and Answers

lightning photo



The answers to these lightning questions have been provided by the National Weather Service.


How powerful is lightning and how fast does it move?


Lightning is a giant spark of electricity. A typical lightning flash contains about 20,000 amps and several hundred million volts. This compares to a standard household current of 15 amps and about 115 volts. Typically, a lightning flash is only 1 to 2 inches wide. The step leader that initiates the lightning flash propagates downward from the cloud at a rate of about 320,000 ft per second or about 220,000 miles per hour. The return stroke (the current that cause the visible flash) moves upward at a speed of about 320,000,000 ft per second or about 220,000,000 miles per hour (about 1/3 the speed of light). In comparison, the sound of thunder travels at about 1100 ft per second or about 750 miles per hour.


How can you tell how far a flash of lightning is away from you?


While you see the visible flash of lightning almost instantaneously, the sound of the thunder travels at a speed of about 1100 feet per second or about 1 mile in 5 seconds. For every 5 seconds between the time you observe the lightning and the time you hear the thunder, the lightning flash is 1 mile away. If it takes 10 seconds between the lightning flash and the thunder, the lightning flash was 2 miles away. For 15 seconds, the flash would be three miles away. Unfortunately, this method only works for the previous flash and does not tell you how close the next lightning strike will be. Generally, if you hear thunder, you are within striking distance for the next flash of lightning. If you are not in a safe place at the time, move to a safe place immediately.


Are there any signs that a lightning strike is imminent?


Sometimes, but not always. In either case, there is little, if any, time to take action to protect yourself. Some of the signs include:

  1. Your hair stands on end (as charges from the ground surge to the top of your head)
  2. You hear a distinctive snapping or crackling sound (small discharges of static electricity may occur in an area where lightning is about to strike)
  3. You experience a tingling sensation (electrical charges may be moving through your body)
  4. There is a sudden increase in the static on portable electronic devices (electrical charges may be moving through the devices, and
  5. An abnormal burning smell in the air (static discharges within the air give off an unusual odor)

If you see any of these signs, lightning is about to strike you or somewhere very near you. It is extremely important that you plan ahead to avoid this situation. You could be killed at any instant.


Is it safe to talk on a cordless phone during a thunderstorm?


Compared to talking on a corded phone, the cordless phone is much less of a hazard. However, there is a momentary risk of being struck by lightning when the phone is being removed from the cradle. Once out of the cradle, it is safe to use a cordless phone during a thunderstorm, provided, of course, that you are in a safe place.


What are the chances that a person will be struck by lightning during his or her lifetime?


Based on documented cases of lightning deaths and injuries, the nationwide odds of being killed or injured by lightning are estimated to be about 1 in 400,000 for each year of your life. Assuming a life span of 80 years, that's lifetime odds of more than 1 in 5000. Keep in mind, though, that your behavior around thunderstorms will determine your individual odds. If you are aware of all the threats posed by lightning and act accordingly, your chances for being struck by lightning will be considerably lower. On the other hand, if you are not aware of those dangers or don't take the appropriate safety precautions, your odds of being struck by lightning will be higher.

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