ery thunderstorm produces lightning. 
Other associated dangers of thunderstorms include tornadoes, strong
winds, hail, and flash flooding.  Flash flooding is responsible
for more fatalities  more than 140 annually  than any other
thunderstorm-associated hazard.

Some thunderstorms do not produce rain that reaches the ground. These
are generically referred to as dry thunderstorms and are most prevalent
in the western United States.  Known to spawn wildfires, these
storms occur when there is a large layer of dry air between the base
of the cloud and the ground.  The falling raindrops evaporate,
but lightning can still reach the ground. 

 

 

 

What to do before thunderstorms approach

Know the
terms used by weather forecasters:

Severe Thunderstorm Watch 
Tells you when and where severe thunderstorms are likely to o</span><span
class="Normal--Char" style=" letter-spacing: 0pt;">ccur.  Watch
the sky and stay tuned to radio or television to know when warnings
are issued.  
Severe Thunderstorm Warning 
Issued  when severe weather has been reported by spotters or indicated
by radar.  Warnings indicate imminent danger to life and pr</span><span
class="Normal--Char" style=" letter-spacing: 0pt;">operty to those
in the path of the storm.

Know thunderstorm
facts:

Thunderstorms may occur singly, in clusters, or in lines.
Some of the most severe weather occurs when a single thunderstorm
affects one location for an extended time.
Thunderstorms typical</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">ly produce heavy rain for a brief period, anywhere from 30 minutes
to an hour.
Warm, humid conditions are very favorable for thunderstorm development.
A typical thunderstorm is 15 miles in diameter and lasts an average
of 30 minutes.
Of the estimated 100,0</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">00 thunderstorms each year in the United States, about 10 percent
are classified as severe.
A thunderstorm is classified as severe if it produces hail at least
three-quarters of an inch in diameter, has winds of 58 miles per hour
or higher, or produces a t</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">ornado.

Know the
calculation to determine how close you are to a thunderstorm:

Count the number of seconds between a flash of lightning
and the next clap of thunder.  Divide this number by 5 to determine
the distance to the lightning in miles.

Remove dead or rotting trees
and branches that could fall and cause injury or damage during a severe
thunderstorm.

If a Tornado Warning is issued, take shelter immediately.When
a thunderstorm approaches, secure outdoor objects that could blow away
or cause damage. Shutter windows, if possible, and secure outside doors.
If shutters are not available, close window blinds, shades, or curtains.

Lightning

T</sub></span><span class="Normal--Char" style=" letter-spacing: 0pt;
">he ingredient that defines a thunderstorm is lightning.  Since
lightning creates thunder, a storm producing lightning is called a thunderstorm. 

Lightning occurs during all thunderstorms.  Lightning results
from the buildup and discharge of electrical energy between positively
and negatively charged areas.

The unpredictability of lightning increases the risk
to individuals and property.  In the United States, an average
of 300 people are injured and 80 people are killed each year by lightning. 
Although most lightning victims survive, people struck by lightning
often report a variety of long-term, debilitating symptoms, including
memory loss, attention deficits, sleep disorders, numbness, dizziness,
stiffness in joints, irritability, fatigue, weakness, muscle spasms,
depression, and an inability to sit for a long period of time.

When thunderstorms threaten your area, get inside a home, building
or hard top automobile (not a convertible) and stay away from metallic
objects and fixtures.

If you are inside a home:

Avoid showering or bathing.  Plumbing and bathroom fixtures can
conduc</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">t electricity.
Avoid using a corded telephone, except for emergencies. Cordless and
cellular telephones are safe to use.
Unplug appliances and other electrical items such as computers and
turn off air conditioners. Power surges from lightning can cause se</span><span
class="Normal--Char" style=" letter-spacing: 0pt;">rious damage.
Use your battery operated NOAA Weather Radio for updates from local
officials.

If outside, with no time to reach a safe location, follow these recommendations:

In a forest, seek shelter in a low area under a thick growth of small
trees.
In o</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">pen areas, go to a low place such as a ravine or valley.  Be
alert for flash floods.
Do not stand under a natural lightning rod, such as a tall, isolated
tree in an open area.
Do not stand on a hilltop, in an open field, on the beach or in a
boat on the wa</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">ter.
Avoid isolated sheds or other small structures in open areas.
Get away from open water.  If you are boating or swimming, get
to land and find shelter immediately.
Get away from anything metal 
tractors, farm equipment, motorcycles, golf carts, golf clubs and bicycles.
Stay away from wire fences, clotheslines, metal pipes, rails and other
metallic paths that could carry lightning to you from some distance
away.
If you feel your hair stand on end (which indicates that lightning
is about to strike), s</span><span class="Normal--Char" style=" letter-spacing: 0pt;
">quat low to the ground on the balls of your feet.  Place your
hands over your ears and your head between your knees.  Make yourself
the smallest target possible and minimize