What You Need to Know About Lightning

Lightning Safety:

In the United States there are about 25 million cloud-to-ground lightning strikes each year.  Each of these strikes is a potential killer.

Lightning is nature’s second-most deadly, thunderstorm-related force - killing an average of 62 people per year.  This is second only to flooding.  Additionally, hundreds of people are injured each year from lightning strikes, and many of these go unreported.  Injuries range from burns to memory loss to nerve damage and can be long-term and debilitating.  Although lightning is a deadly force, about 90% of strike victims can survive if they receive imminent medical attention.

If a person is struck by lightning, immediately call 911 and begin administering CPR if necessary.  You are in no danger of receiving a shock from a lightning victim.

You are in danger of a lightning strike even when the storm is not overhead.  Lightning can strike as far as 10 to 20 miles away from the source, with blue sky above.  If you can hear thunder, then you are close enough to be struck by lightning and should take shelter immediately!

In Wisconsin, on average, about one person dies each year from a lightning strike.


Lightning Picture

Outdoor safety:

   Taking shelter under a tree is one of the most dangerous actions you can take during a thunderstorm.  Many victims of a lightning strike are not struck by the visible flash, but by the current that travels along the surface of the ground.  There is no safe place outdoors during a thunderstorm!  You should get indoors immediately.

   Some extremely dangerous outdoor activities during a thunderstorm include:  boating, swimming, fishing, bicycling, golfing, camping, and walking.  If an organized outdoor sport is taking place when lightning threatens, the activity should be stopped immediately so that participants and spectators have sufficient time to get to safety before the lightning risk becomes significant.

   If no shelter is available, avoid being the highest point around, but do not lie flat on the ground.  Squat on the balls of your feet, and put your hands over your ears and your head between your knees.  The goal is to be as low as possible while minimizing contact with the ground.


Indoor safety:

   Even indoors you are not completely safe from a lightning strike.  You can reduce your risk by avoiding any appliances that are directly connected to either electricity or plumbing. 

   Some dangerous activities include talking on a corded phone, using a computer, and taking a shower.  Also, avoid contact with concrete walls and floors which may contain metal reinforcing bars.

   You should also stay away from all windows and doors.

Observe the 30/30 rule:  The first 30 means that if the gap of time between the flash of lightning and the boom of thunder is 30 seconds or less, you are in danger and should take shelter immediately.  The second 30 means you should wait 30 minutes after the last sounds of thunder before resuming outdoor activities.                                             

Lightning Science:

At any given moment, there are 1,800 thunderstorms in progress somewhere on earth.  This amounts to 16 million storms each year!

Lightning often reaches temperatures of 54,000 degrees Fahrenheit – several times hotter than the surface of the sun!  It rapidly heats the air around it, causing the air to expand so quickly it results in a shock wave that we hear as thunder.

A good way to estimate the distance to a storm is to count the seconds between when you see the lightning and hear the thunder.  If you divide this number by 5, you can find out how many miles away the storm is.  This works because we see the lightning instantaneously, but sound can only travel a fifth of a mile per second.  So, thunder travels one mile in five seconds.

The development of ice crystals in a cloud is the key to building up the charges required for the formation of lightning.  When these ice crystals get caught in updrafts and downdrafts, they rub up against each other and cause a separation of charges.  Positively charged ice particles rise to the top of the cloud while the negatively charged particles sink to the bottom. 

While most lightning originates from the bottom, negative part of the cloud, some originates in the top, positive portion of the cloud.  This is called positive lightning and is particularly dangerous for several reasons.  It frequently strikes away from the rain in the thunderstorm, so areas 5 to 10 miles ahead and behind the storm are in danger of lightning strikes.  Also, positive lightning typically has a longer duration and therefore a greater potential to ignite fires.  Finally, positive lightning strikes have a higher electrical current, which makes it more dangerous for a potential strike victim.

For additional information visit:       http://www.nssl.noaa.gov/edu/safety/lightning.html                        http://www.lightningsafety.noaa.gov/

...Melissa Peterson, Student Volunteer

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