When Lightning Strikes

by Betsy Crisp, Extension Agent IV, M.S., L.D.
Extension Family and Consumer Sciences

The earth experiences about 44,000 thunderstorms every day, with approximately 1,800 storms in action at any given moment.  The most active area in the world is Java, an island of Indonesia, with an average of 223 storm days per year.

Florida is known as the lightning capital of the United States, with storms occurring approximately 100 days out of the year, compared to California's low of only 5.  Although our entire state rates as a high risk area, the most dangerous area runs from St. Augustine (north) to Lake Okeechobee (south) and from east to west coasts.  That puts our Tampa Bay area right in the middle of the danger zone.  Daily summertime showers are a fact of life in Florida but should not be taken for granted.  Florida ranks number one in the number of deaths due to lightning, 94% of which occur between late May and end of September.  An average of 100 people are killed in the U.S. each year (10-13 in Florida) and almost 600 injured (30 in Florida).  Lightning kills more people in the U.S. than hurricanes and tornados combined.
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WHY FLORIDA?  Partially due to its high heat levels, high humidity, and location between the Gulf and Atlantic oceans;  rain clouds plus high heat equals thunderstorms and lightning!
As Ben Franklin first proved in 1760 with just a kite, string, and a key:  lightning is electricity.  There are three basic kinds of lightning:  1) cloud-to-cloud;  2) cloud-to-ground; and 3) intra-cloud.  Charged particles gather in the lower part of the clouds and are attracted to charged particles on the ground.  If the earth's particles are positively charged and the cloud's are negative, the static electricity causes a spark to jump from the cloud to the ground.  If the opposite occurs, a positive spark spikes up to meet the negative cloud (usually seen at the front edge of the storm).  Either way, when these sparks collide, a sort of short circuit occurs and causes the bright flash we know as lightning.  In the latter example, the strike is three times hotter and many times starts a fire.  Lightning travels at the speed of light (186,000 miles per second).  This quick blast of energy only lasts just a few millionths of a second, up to 100 million volts, and reaches a peak temperature of 60,000 degrees Fahrenheit.  As a result, the air around it is super-heated and causes shock waves that crash together producing loud booms we know as thunder.  Thunder travels at the speed of sound (1,090 feet per second)  Therefore, it takes about five seconds to travel a mile.  A single bolt of lightning can discharge about 100 million bolts of electricity and can travel as far a 10 miles from a cloud.
"Divide by 5" rule:  You can determine the distance between yourself and a thunderstorm by counting the time, in seconds, between the lightning flash and the thunder, and dividing by 5; i.e., if thunder is heard 10 seconds after the flash, the storm is about two miles away.  Play it safe...if you can hear thunder, generally, you are within striking range?
When viewed from a safe distance, a thunderstorm is one of nature's most awesome and beautiful displays.  When you get caught by surprise and are forced to watch it "close up and personal," it can be a very frightening and even deadly experience!
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PROTECT YOURSELF

In a study by the Lightning Protection Institute (LPI), it shows that more lightning casualties occur at home.  Out of 1,000 incidents, most occurred (in descending order):

1.  on the telephone
2.  in the kitchen
3.  doing laundry
4.  watching television
5.  at a door or open window

PROTECT YOUR HOME

In another three-year study by LPI, damages to unprotected houses were examined.  Results showed the following strike points, in descending order of frequency:

1.  roof and projections
2.  television antenna
3.  overhead power line
4.  adjacent tree

The Lightning Protection Institute recommends the following protection standards:
  1. Lightning rods - a maximum of 20 feet apart on high points of the roof and projections
  2. Main conductors - of heavy copper or aluminum cable, interconnecting rods and grounds
  3. Bonds to metal bodies - to prevent sideflash
  4. Lightning arresters - to protect wiring and appliances from surges following powerlines
  5. Tree protection - for any tree taller than the house and within 10 feet
  6. Grounds - a least two half-inch diameter copper-clad rods sunk ten feet deep in clay soil and special grounding in sand, gravel, or rocky soil
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PROTECT YOUR TREES

Lightning is hard on trees.  Thousands of trees are struck by lightning each day.  Trees are usually the tallest objects in the landscape.  Their deep roots make them nature's natural lightning rods, able to easily pass electric current from the air down into the ground.

Taller trees are more likely to be hit, not only because of their height but also because they are more likely to suffer root or stem decay.  As a result, the plant tissue is wetter and makes a better conductor.  Lightning is nature's way of eliminating old, sick trees.  Lightning damage may be minor or severe.  Often, damaged trees become victims of further damage from insects, diseases, or wind.

INTERESTING FACTS

  • Lightning is five times hotter than the sun's surface.
  • Lightning hits each square mile in Central Florida 40 times a year.
  • There can be as many as 500 cloud-to-cloud strikes within a 45-minute storm.
  • The average flash could light a 100-watt light bulb for more than 3 months.

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  • MYTH VERSUS FACT

    Myth - Lightning never strikes in the same place twice.
    Fact - The Empire State Building is struck about 23 times in an average year.

    Myth - In medieval times church bells were rung during thunderstorms, because people thought the sound waves from the bells would suppress the lightning.
    Fact - This belief was discarded when one historian noted that in a 33-year period, 386 church towers were struck and 103 bellringers killed.

    Myth - Lightning follows the most direct path to the ground.
    Fact - It has been known to travel through clear air and strike 10 miles from the storm like a "bolt from the blue!"

    Myth - Rubber-soled shoes protect you from a lightning shock.
    Fact - It is unreasonable and suicidal to think that something so powerful as lightning can be stopped by a half-inch of rubber.

    Myth - Rubber tires on a car protect you from the strike.
    Fact - Actually, it's not the tires.  The metal body conducts the current around you, to the ground, providing windows are rolled up and you are not touching the metal.   Not the case if it's a convertible, utility, or 4x4 vehicle with a fiberglass roof!

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