T h e U n d e r r a t e d K i l l e r
BUREAU OF PUBLIC SAFETY
The Striking Facts:
It is estimated that at any given moment nearly Lightning usually kills more people each year than do
2,000 thunderstorms are in progress over the tornadoes and hurricanes combined. Occasionally, flash
earth’s surface, and lightning strikes the earth floods will kill more people. Lightning fatalities are not
100 times each second. There are about 45,000 publicized as often as hurricane and tornado deaths. Lightning
thunderstorms daily and 16 million annually deaths usually happen one or two at a time while several may
around the world. There are at least 100,000 be killed during a tornado or hurricane event.
thunderstorms annually across the United
States. Since 1940, lightning has killed close The first strike of lightning from a thunderstorm may be
to 9,000 people. Since 1959, Florida has had the most dangerous, not in terms of impact, but
more lightning deaths than any other state. because of the element of surprise. In Santa
In a ten year period, approximately 75 deaths Rosa County, three men were standing
were reported in Florida from lightning, June, under a tree with a dark storm cloud
July and August are by far the highest casualty in the distance. The first strike from
months with an average of 17 deaths occurring. the distant storm hit the tree and
eventually killed all three. A boy
Northwest Florida averages 75 thunderstorms a swimming near Fort Pickens
year. The west central part of the state leads the was struck by lightning from a
country in frequency of thunderstorm days each storm that was occurring over
year with more than 100. the mainland. Luckily, he lived
but was severely injured. In Bay
County, a family outing turned
into a disaster when two boats were
trying to get to shore ahead of an
approaching thunderstorm. Lightning
struck the boats killing two people.
The graph below (left) shows the months
most prevalent for lightning fatalities.
The Florida map below (right) shows the distribution of
lightning fatalities by county.
What Causes Lightning?
There are different kinds of lightning: within clouds, between How Thunderstorms Develop:
clouds, and from clouds to clear air. The lightning that As thunderstorms develop, interactions
concerns people most goes from cloud to the ground, as of charged particles produce an intense
seen in the pictures above. These flashes start fires, splinter electrical field within a cloud. A large
trees, knock out electric power and even kill people. Cloud positive charge is usually concentrated
to ground lightning represents only about 20 percent of all in the frozen upper layers of the cloud;
lightning strikes. a large negative charge, along with a
smaller positive area, is found in the lower
Here is what happens: Negatively charged portions.
electrons zigzag downward in a forked
pattern known as a stepped leader. As As the thunderstorm passes over the
this stepped leader nears the ground, ground, the negative charge in the base of
it draws a stream of positive charges the cloud induces a positive charge on the
upward, usually through something ground below and for several miles around
high such as a tree. As the leader the storm. The ground charge follows the
and streamer come together, a storm like an electrical shadow, growing
powerful electrical current begins stronger as the negative cloud charge
flowing and the return stroke increases.
begins with an intense wave of
positive charges traveling upward The attraction between positive and
about 60,000 miles per second negative charges make the positive
(about one-third the speed of light). ground current flow up buildings, trees
This is the light that we see. The and other elevated objects in an effort
process can repeat several times in to establish a flow of current, but air – a
less than half a second, making lightning poor conductor of electricity – insulates
flicker. the cloud and ground charges, preventing
a flow of current until huge electrical
What Causes Thunder? charges are built up. Lightning flashes
Average lightning strikes produce currents of 30,000 when the attraction between positive and
amperes, although some may approach 100,000 amperes. The negative charges become strong enough
rapid rise in current produces temperatures in the lightning to overcome the air’s high resistance to
channel of more than 50,000º F which causes the air in the electrical flow.
channel to expand. The expanding air cools, then contracts.
This rapid expansion and contraction starts air molecules
moving back and forth, making sound waves we hear as
thunder (much like the sound a paper bag makes when you
blow it up and pop it—the air expands quickly making a loud
bang). When a lightning bolt flashes through the sky, we see
it instantly. Thunder (the sound that lightning creates) takes a
few seconds to reach us.
Sound travels a mile in about
five seconds. Start counting
when you see the lightning,
if you hear the thunder in
five seconds, the lightning is
a mile away; in ten seconds
the lightning is two miles
away and so on. If you see the
lightning and hear the thunder
at the same time, the lightning
is directly over head. Thunder
Staying Safe During sometimes rumbles because
Thunderstorms: we hear it first from the flash
nearest us, then from other parts of the flash farther away.
• If you’re outside, get inside a building
or inside an all metal (not a convertible) When there is no shelter, avoid the highest objects in the
vehicle. area. If only isolated trees are nearby, your best protection is
to crouch in the open, keeping twice as far away from isolated
• Stay indoors and do not venture outside, trees as the trees are high. Get out of the water, off small
unless absolutely necessary. boats, and off beaches. The safest place is an automobile until
the storm passes. If you are caught aboard a boat, crouch
• Stay away from open doors and windows, down in the center of the boat, away from metal hardware
fireplaces, stoves, metal pipes and plugged- such as fishing poles. Golfers using golf clubs and wearing
in electrical devices. cleated shoes are particularly good lightning rods. If you
happen to get caught outside and you feel your hair stand on
• Don’t use pools, hot tubs, bath tubs, end, lightning may be about to strike you. Frequently, two or
showers, sinks or other plumbing fixtures. three seconds before lightning strikes, your hair may stand
on end. Crouch over and make yourself as small an area
• Turn off the television and avoid using as you can. Do not lie down as the wet ground can carry the
corded telephones or computers during a lightning.
Persons struck by lightning receive a severe electrical shock
• Wait 30 minutes after the last clap of and may be burned, but they do not carry an electrical
thunder before venturing outside. charge and can be handled safely. A person killed by
lightning can often be revived by prompt first aid medical care
For more information contact: (CPR, mouth to mouth).
Do not become another lightning statistic. When dark
clouds are around, lightning is seen or thunder is heard,
get inside and stay safe.
Division of Emergency Management
6575 North “W” Street
Pensacola, Florida 32505