Lightning has fascinated and excited humans for as long as they
have watched the skies. Although
meteorologists understand the cloud
conditions necessary to produce it, lightning cannot be forecasted. At
any moment, there are as many as 1,800 thunderstorms in progress
somewhere on Earth, and each is producing deadly lightning. Lightning
detection systems in the U.S. see an average of 25 million strokes of
lightning each year, from some 100 thousand storms. It is estimated that
the Earth is struck by 100 lightning bolts every second.
The clouds at the high levels of the thunderstorm are made of ice
crystals. The formation of ice in a cloud is an important element in the
development of lightning. Those storms that fail to produce large
numbers of ice crystals may also fail to produce a lot of lightning.
Strong rising and sinking motions within the cloud are important too, as
they enhance collisions among cloud particles 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 middle and lower parts of the storm.
As the differences in charges continue to increase, positive
charges rise up taller objects such as trees, houses, and telephone
poles. The charge can also move up you, causing your hair to stand on
end! This is natures way final way of warning you that lightning can
strike near you very soon.
If the negatively charged area at the bottom of the storm gets large enough, sends out a channel toward the ground called a step leader.
It is invisible to the human eye and moves in steps toward the ground.
When the step leader nears the ground, or a target like a radio tower,
it repels all the negatively charged in the surrounding area, and
attracts all the positive charge. As the positive charges collect in
high enough concentration, they send out small bolts of ground to air
lightning called streamers. If the streamers can make contact with the
step leader, an electric current wave propagates up the channel as a
bright pulse -- lightning!
And of course, with lightning comes thunder. Lightning heats the
surrounding air to as much as 50,000 degrees Fahrenheit, which is five
times the temperature of the surface of the sun! When air is heated, it
expands, and this expansion is what's causing the sound of thunder. The
expansion is happening faster than the speed of sound, which creates a
sonic boom.
Lightning Medical Impacts
Lightning usually claims only one or two victims at a time and
usually does not cause the mass destruction left in the wake of
tornadoes or hurricanes. Lightning generally receives less attention
than any other weather hazard.
During a thunderstorm, each flash of cloud to ground lightning is a
potential killer. However, lightning deaths can be prevented if people
are aware of the dangers and seek shelter.
Lightning can strike as much as 10 miles away from the rain area in
a thunderstorm. That is about the distance that you are able to hear
the thunder from the storm. If you can hear the thunder from a storm,
you are close enough to be struck by lightning.
Where organized sports activities are taking place, coaches,
umpires, referees, or camp counselors must protect the safety of the
participants and spectators by stopping the activities so that
participants and spectators can get to a safe place before the lightning
threat becomes significant.
Lightning Facts
- An average of 85 lightning fatalities occur each year
- Approximately 10% of the people struck by lightning are killed
- 70% of lightning strike victims suffer long-term effects
- Approximately 400 people survive lightning strikes each year
- The primary cause of death from lighting is cardiac arrest
- Unlike high voltage electrical injuries with which massive internal tissue damage may occur, lightning seldom causes substantial burns
- Most lightning injuries and deaths can be prevented with advance planning and being aware of developing weather situations
- A NOAA Weather Radio can help keep you informed with the latest thunderstorm information
Lightning Safety
Being outdoors is the most dangerous place to be during a lightning
storm. The National Weather Service advises that when you hear thunder
or see lightning to quickly move indoors or into a hard topped vehicle
and remain there until well after the storm has passed.
Any location is dangerous durning a lightning storm, however, some
areas are more dangerous than others. Some of the riskiest locations
include:
- Anywhere near the water:
- Boating
- Fishing
- Swimming
- Activities on the beach
- Areas near tall trees (especially isolated trees):
- Golf course
- Picnic areas
- Hiking trails
- High terrains such as hill tops and ridges
- High places such as house roofs during construction
- Open areas like fields
Outdoor Safety Rules
Knowing outdoor safety rules can help save your life or that of loved ones.
When lightning approaches, get inside a completely enclosed
building. Car-ports, open garages, storage sheds, metal sheds, and
covered patios are not safe shelters.
If no enclosed building is available, get inside a hard-topped, all metal vehicle.
Get out of the water! Get off the beach and out of small boats and
canoes. If caught in a boat, crouch down in the center of the boat away
from metal hardware. Avoid standing in puddles of water, even if wearing
rubber boots.
If you cannot reach shelter, avoid being the tallest object in the area. Do not take shelter under a tree. If you are in the woods, find shelter under the shortest trees.
If only isolated trees are nearby, crouch on the balls of your
feet. A rule of thumb to follow is to stay twice as far away from a tree
as it is tall. Don't lie on the ground.
Avoid leaning against vehicles and get off bicycles and motorcycles.
Indoor Safety Rules
When lightning strikes a building, house or other structure, it
follows metal conductors such as electrical wiring, plumbing, and
telephone lines from the structure to the ground. When this process
occurs, it usually leaves the inhabitants unharmed.
Once lightning enters the home it can surge through the electrical,
phone, plumbing, and radio/television reception systems. It can also
travel through any metal wires or bars in concrete walls or flooring as
well as windows and doors. It is important to avoid these conductors
during an electrical storm.
Phone use is the leading cause of lightning injuries within the
home. Lightning can travel long distances in both phone and electrical
wiring, especially in rural areas where other conductors are limited.
Basements should be used with caution during
lightning storms (unless there's a tornado warning!) because they
usually contain conductors. Avoid contact with washers and dryers since
they not only have contacts with the plumbing and electrical systems,
but also have an electrical path to the outside through the dryer vent.
Concrete floors should also be avoided as they usually contain some form
of reinforcement which can easily become electrified by a nearby
lightning strike. Avoid bathing during a lightning storm as the household plumbing can carry a deadly current.
