Updated AMS Recommendations for Lightning Safety - 2002
Reprinted from the American Meteorological Society Website
INTRODUCTION: Lightning has been the second greatest
cause of storm-related deaths (after floods) in the United
States during the past 40 years. Fortunately, however, through
public awareness and the applications of safety guidelines,
the vast majority of lightning casualties (deaths and injuries)
can be easily avoided. The American Meteorological Society
has recently approved a Statement on Lightning Safety Awareness
(www.ametsoc.org/AMS) which exhorts all citizens, but especially
those responsible for the safety of groups engaging in outdoor
activities, to further their awareness of lightnings safety
issues. The National Weather Service, in conjunction with
cooperating organizations including the Red Cross, has initiated
a Lightning Safety Awareness Week (www.lightningsafety.noaa.gov).
This paper provides supplemental information to the AMS Statement
as well as assembles background materials benefiting all involved
in lightning safety awareness activities. It also serves as
an update to a review of the topic published in the Bulletin
in 1999 (Holle et al., 1999).
Lightning kills more people each year on average than hurricanes
and tornadoes combined. When corrected for underreporting,
there are about 100 lightning fatalities annually in the United
States (Cherington et al., 1999). Beyond the tragic loss of
life, however, are the many injuries. Only about 10% of lightning
strike victims are killed; 90% survive. But many of the estimated
1000 survivors suffer severe, life-long injury and disability.
It is common for people to refer to the chance of being struck
by lightning as an improbable or unlikely event. Yet actual
statistics say otherwise. Lightning strikes the ground approximately
25 million times each year in the United States (Orville and
Huffines, 2001). Most people greatly underestimate the probability
of being involved in a lightning strike. According to the
National Weather Service, the chance of an individual in the
United States being killed or inured during a given year is
one in 240,000. Assuming an average life span of 80 years,
a person's odds over their lifetime becomes one in 3000. Assuming
the average person has ten family members and others with
whom they are close, then the chances are one in 300 that
a lightning strike will closely affect a person during their
Although absolute personal protection from lightning cannot
reasonably be achieved, following a set of simple guidelines
can substantially reduce lightning casualties. The vast majority
of lightning casualties can be avoided through improved public
education. The public needs to be made aware of the magnitude
of the lightning hazard and motivated to practice lightning
safety. The following background information will provide
some insights into issues related to lightning safety, including
the physics of lightning, lightning climatology, lightning
casualty demographics, and the medical aspects of lightning
LIGHTNING PHYSICS. Lightning can strike
many kilometers from the parent thunderstorm, well outside
the rain area and even beyond the visible thundercloud (Lopez
and Holle, 1999). Lightning can also strike from debris clouds
several tens of minutes after the parent thunderstorm has
decayed. Thus lightning safety requires a large standoff distance
from thunderstorms and a long standoff time after apparent
Lightning does not "decide" where it will strike until the
stepped leader descending from the cloud is about 30 m from
the ground or object that is struck. Thus, short objects in
an open area can be struck by lightning even if a tall object
is nearby. If lightning strikes a nearby object, shock can
result either by direct contact or a side flash. If lightning
strikes the ground, the high voltage gradients cause currents
to flow in concentrated channels on the surface or within
the soil, and can injure people nearby. The associated step
voltages and surface arcs, respectively, can be deadly more
than 40 m from the lightning strike point. In addition, there
can be upward discharges tens of meters in length from tall
objects (including people) that are located within tens of
meters from the strike point.
Thunder produced by a lightning strike travels one mile (1.6
km) every five seconds. Thus, counting the number of seconds
between the visible "flash" and the audible "bang" and dividing
by 5, provides the distance in miles. In noisy urban areas,
thunder may not be audible more than a few miles from the
flash, and is rarely heard for distances of more than 10 miles
(16 km) even in the most quiet environments. The distance
between successive lightning strikes in some thunderstorms
can be as large as 5 miles (8 km) -- at times even more.
LIGHTNING CLIMATOLOGY. The average
areal density of cloud-to-ground lightning flashes in the
contiguous United States has been objectively measured by
the National Lightning Detection Network (NLDN). The greatest
flash density is found in central Florida, where each square
kilometer is struck more than ten times each year. High flash
densities are also found throughout the Southeast and Midwest.
Almost half the nation has a flash density greater than 4
flashes per square kilometer per year. No place in the United
States is totally free of a lightning threat. Also, the annual
average flash density can be misleading. Some places may have
a low flash density over 12 months, but a high peak seasonal
value. For example, for a few weeks in summer, the Front Range
of the Rocky Mountains in Colorado approaches the flash density
of Florida. Also, some intense mesoscale convective systems
can unleash more than 100,000 flashes during their life span
while traversing several states.
While lightning can occur anywhere and anytime during the
year, lightning activity has a strong annual cycle in the
United States. The lightning rate shows a broad peak in summer
centered on July, with a rapid increase during May and a rapid
decrease in September. The lightning flash rate continues
to decrease through winter, with a minimum occurring during
January. Most lightning occurs during the afternoon or early
evening, between 1200 and 2000 LST, peaking at about 1600
LST. Portions of the upper Midwest have a evening or nocturnal
peak between 2000 and 0400 LST (Orville and Huffines, 2001).
LIGHTNING CASUALTY DEMOGRAPHICS. Lightning
casualty statistics reflect geographical differences in lightning
strike density, population density, outdoor activity levels
and public lightning threat awareness. Casualties occur most
often during July, and between 1200 and 1800 LST, with the
peak around 1600 LST. Sunday has the most casualties, followed
closely by Saturday. Late afternoon is the deadliest period.
Males are struck by lightning in significantly greater numbers
than females. These factors presumably reflect higher rates
of outdoor exposure.
The relative frequency of lightning casualties in the United
States by location or activity is listed in Table1. When lightning
is imminent or occurring, avoid these activities like your
life depends on it -- it does. The studies from which these
results are taken did not include higher elevation as a factor.
Though not listed here, higher elevation produces an enhanced
risk when thunderstorms threaten.
Many lightning casualties occur before the thunderstorm rains
have moved into the area. The casualty rate actually decreases
while the rainstorm is in progress and people seek inside
shelter -- from the rain. Even larger numbers of casualties
occur after the rain dissipates. People, in too much of a
hurry to go back outside, ignore the fact that lightning continues
to be a threat outside the precipitation areas.
In terms of absolute numbers of lightning casualties, the
top five states are, in order: Florida, Michigan, Pennsylvania,
North Carolina, and New York. But a more meaningful measure
is the number of lightning casualties per capita; the top
five states become, in rank order: Wyoming, New Mexico, Florida,
Arkansas, and Colorado. The Rocky Mountains states have both
relatively low annual lightning flash and population densities,
yet many people tend to be outside precisely when the lightning
hazard is at its greatest. The degree of outdoor at-risk behavior
in occupation and recreation, combined with poor public awareness
can lead to distressingly high casualty rates. All states
have some degree of lightning threat and all persons should
be aware of the need for and practice lightning safety.
MEDICAL ASPECTS OF LIGHTNING. Medical
authorities have recently been learning more about the range
of impacts of lightning on its victims (Cooper, 1995). The
medical aspects of lightning are detailed on several of the
websites listed in Table 1, and a few key highlights are presented
here. If there are lightning casualties, immediately calling
"9-1-1" for assistance is paramount. Death results from cardiac
arrest and/or stopped breathing at the time of the strike.
First aid for lightning strike victims is CPR or mouth-to-mouth
resuscitation, respectively. Medical authorities recommend
that if numerous persons are involved in a lightning incident,
treat the apparently dead first -- as many can be revived.
While only about one in ten of those struck by lightning now
die, lightning victims often suffer severe, life-long debilitation.
These injuries are primarily neurological, with a wide range
of symptoms, and are sometimes difficult to diagnose. The
most frequent symptoms are memory deficit, sleep disturbance,
chronic pain, dizziness, and chronic fatigue. These symptoms
may not appear or be recognized until some time after the
lightning injury, sometimes months after the initial injury.
Lightning survivors sometimes have trouble processing information,
are easily distracted, and have personality changes. These
impair their ability to earn a living and maintain relationships,
which exacerbates the psychological problems lightning survivors
often have in dealing with their injuries. Family, friends,
and colleagues need to continue providing emotional support
and not abandon or isolate them. "Lightning Strike Electric
and Shock Survivors International" is the main support group
for lightning survivors and provides an invaluable service.
BASIC LIGHTNING SAFETY GUIDANCE. The following guidelines
have been compiled by lightning safety experts and reflect
the current thinking on this topic. Please note the knowledge
base on lightning is continuously expanding so readers are
advised to keep abreast of new developments as they occur.
The National Weather Service routinely issues watches and
warnings for thunderstorms that can produce tornadoes and
other severe weather (high winds and large hail). It does
not, however, issue warnings based solely upon lightning.
Moreover, a storm need be neither tornadic nor severe in order
to produce copious numbers of lightning strikes. When considering
lightning any thunderstorm, by definition, has the potential
to produce a "severe" lightning strike. While adhering to
lightning safety rules can at times be inconvenient, one must
consider the alternative of not following these simple measures.
Adults are responsible for the safety of children under their
care; this includes matters of lightning safety. In this spirit,
the National Collegiate Athletic Association (NCAA) has issued
guidelines for lightning safety for those in charge of team
sports. K-12 educators have become active in promoting lightning
safety on schools (Roeder et al., 2001). Ultimately each of
us is responsible for our own safety during lightning storms.
The most important fact is to realize that no place outdoors
is safe when thunderstorms are nearby. Implementing a lightning
safety and awareness plan is a multi-level process:
Level-1: If you are planning outdoors activities, obtain
the weather forecast beforehand. Schedule outdoor activities
around the weather to avoid exposure to the lightning hazard.
Know your local weather patterns.
Level-2: If you are planning to be outdoors, identify and
stay within travelling range of a proper shelter. [30-30 rule deleted. No longer in use]
Level-3: When lightning threatens, go to a safer location.
Do not hesitate. The lightning casualty lore is replete with
tales of persons just about to make it to safety when they
were struck. Even a few extra minutes lead time can be life
What is a safer location? The safest place commonly available
during a lightning storm is a large, fully enclosed, substantially
constructed building, e.g. your typical house, school, library,
or other public building. Substantial construction also implies
the building has wiring and plumbing, which can conduct lightning
current safely to ground. However, any metal conductor exposed
to the outside must not be touched precisely because it could
become a lightning conduit. Once inside, stay away from corded
telephones, electrical appliances, lighting fixtures, ham
radio microphones, electric sockets and plumbing. Don't watch
lightning from open windows or doorways. Inner rooms are generally
preferable from a safety viewpoint.
If you can't reach a substantial building, an enclosed vehicle
with a solid metal roof and metal sides is a reasonable second
choice. As with a building, avoid contact with conducting
paths going outside. Close the windows, lean away from the
door, put your hands in your lap and don't touch the steering
wheel, ignition, gear shifter or radio. Convertibles, cars
with fiberglass or plastic shells, and open-framed vehicles
are not suitable lightning shelters.
Level-4: If you cannot flee to a safer location, take action
to minimize the threat of being struck. Proceed from higher
to lower elevations. Avoid wide-open areas, including sports
fields, beaches and golf courses. Avoid tall, isolated objects
like trees, poles, and light posts. Avoid water-related activities
such as swimming (including indoor pools), boating and fishing.
Do not remain in open vehicles like farm tractors, cabless
construction machinery, riding lawnmowers and golf carts (sun
roofs offer no protection). Do not consider unprotected open
structures such as picnic pavilions, rain shelters and bus
stops. Avoid contact with metal fences, metal bleachers, or
other long metal structures. And the cardinal rule remains:
Do not take shelter under trees to keep dry during thunderstorms.
Level-5: If circumstances or a series of bad decisions have
found you outside of a shelter, far removed from a safer place
when lightning is occurring, there are still measures to be
taken. If lightning is about to strike, it will sometimes
provide a very few seconds of warning. Sometimes your hair
may stand on end, your skin will tingle, light metal objects
will vibrate or you will hear a crackling or "kee-kee" sound.
If this happens and you're in a group, spread out so there
are several body lengths between each person. Once you've
spread out, use the lightning crouch. Put your feet together,
squat down, tuck your head, and cover your ears. When the
immediate threat of lightning has passed, continue heading
to the safest place possible.
Level-6: If the worst happens, there are key Lightning First
Aid guidelines. First, if at all possible, call "9-1-1" immediately.
Since all deaths from lightning strikes result from cardiac
arrest and/or stopped breathing, begin treatment as soon as
possible. CPR or mouth-to-mouth-resuscitation is the recommended
first aid, respectively. It is an enduring myth that strike
victims retain electrical charge. They do not. There is no
hazard posed to a care giver. If the storm's lightning is
ongoing and represents a continuing risk to responders, consider
moving the victim to a safer location
No lightning safety guidelines will provide 100% guaranteed
total safety, but the preceding guidelines will greatly minimize
the lightning hazard to humans.
LIGHTNING DETECTION TECHNOLOGY. Hand-held lightning
detectors have become more affordable and more popular in
recent years. While potentially helpful it should be noted
their performances may not been have been independently, rigorously
and objectively verified. There is anecdotal evidence that
some can fail to detect weak and/or intermittent, but still
deadly, lightning. There are also many examples of people
installing and using the detectors incorrectly. Moreover,
these devices should be used only as a back-up to the "30-30
Rule." There are commercial services available which will
provide automatic notifications when lightning has been detected
by the National Lightning Detection Network (NLDN) within
user-specified distances to an activity/site. The alert can
be sent via pager, fax, e-mail or cell-phone. These services
are reasonably priced and can be a useful component of a lightning
safety plan for organized outdoor activities. Alternately,
private forecasting firms can provide tailored lightning alerts
along with additional weather related services. The best detection
technology, however, cannot provide long lead times from a
thunderstorm forming rapidly overhead. Thus, in the end, those
responsible must still watch the sky for developing thunderstorms
and be ready to proceed to a safer location hopefully before
the first lightning is produced.
SUMMARY. Lightning is the
underrated storm-related weather hazard. Until
recently, relatively little attention has been paid to lightning
safety, as compared to tornado, hurricane and flood safety.
Perhaps because its victims often fall one at a time, without
graphic property destruction, it garners less media attention.
Fortunately, the vast majority of lightning's casualties can
be easily, efficiently and inexpensively avoided. Public education
is the key. The public, especially those charged with managing
outdoor activities, must become more aware of the magnitude
of the hazard and become educated about lightning safety procedures.
The meteorological community can play a key role in improving
this aspect of weather safety in the United States and around
the world. We call on professional meteorologists, especially
broadcasters and those in a position to affect the required
changes, to proactively engage the public in lightning safety
education. Lightning Safety Awareness Week, organized by the
National Weather Service in conjunction with partnering organizations,
is an excellent example of an effective public awareness activity.
Table 2 is a compilation of Internet resources that can provide
additional information and support.
Cherington, M., J. Walker,. M. Boyson, R. Glancy, H. Hedegaard
and S. Clark, 1999: Closing the gap on the actual numbers
of lightning casualties and deaths. Preprints, 11th
on Applied Climatology, Dallas, TX, Amer. Meteor.
Cooper, M.A., 1995: Emergent care of lightning and electrical
Neurol., 15, 268-278.
Cummins, K.L., M.J. Murphy, E.A. Bardo, W.L. Hiscox, R.B.
Pyle and A.E. Pifer, 1998: A combined TOA/MDF technology upgrade
of the U.S. National Lightning Detection Network. J.
Geophys. Res., 103 (D8), 9035-9044.
Holle, R.L., R.E. Lopez and C. Zimmermann, 1999: Updated
recommendations for lightning safety - 1998. Bull.
Soc., 80, 2035 - 2041.
Lopez, R. E., and R.L. Holle, 1999: The distance between
successive lightning flashes. NOAA Tech. Memo. ERL NSSL-1XX,
National Severe Storms Laboratory, Norman, OK, 28 pp. [Available
from NSSL, 1313 Halley Circle, Norman, OK 73069.]
Orville, R.E. and G.R. Huffines, 2001: Cloud-to-ground lightning
in the United States: NLDN results in the first decade, 1989-1998.
Rev., 129, 1179-1193.
Roeder, W.P., R. J. Vavreck, F.C. Brody, J.T. Madura and
D. E. Harms, 2001: Lightning safety for schools. Preprints,
on Education, Albuquerque, NM, Amer. Meteor. Soc.,
Contributors to this document:
William P. Roeder*, Staff Meteorologist, 45 WS/SYR, 1201
Edward H. White II St., MS 7302, Patrick AFB, FL 32925-3238
Mary Ann Cooper, MD, Dept. of Bioengineering and Emergency
Medicine, University of Illinois at Chicago
Ronald Holle, Meteorologist, Vaisala-GAI, Tucson, AZ
John Jensenius, Warning coordinator Meteorologist, National
Weather Service Forecast Office, Gray, ME
Jack Jordan, State Farm Insurance Co.
Richard Kithil, Jr., President, National Lightning Safety
Institute, Louisville, CO
E. Philip Krider, Ph.D., Professor, Institute of Atmospheric
Physics, University of Arizona, Tucson, AZ
Rocky Lopes, Ph.D., Manager, Disaster Education, American
Red Cross National Headquarters, Washington, DC
Walter A. Lyons, Ph.D., CCM, FMA Research, Inc , Fort Collins,
James Vavreck, Science Teacher, Henry W. Eggers Middle School,
Katie Walsh, Ed.D, Director of Sports Medicine/Athletic Training,
East Carolina State University, Greenville, NC
Christoph Zimmermann, Lightning Safety Consultant, Wxline,
LLC, Tucson, AZ
* Corresponding Author
Lightning Casualties In The U.S. By Location Or Activity
||Open Areas (including sports fields)
|| Going Under Trees To Keep Dry
||Water Related Activities (swimming, boating,
|| Golfing (while in the open)
||Farm And Construction Vehicles (with open
||Corded Telephone (#1 indoor source of lightning
||Golfing (while mistakenly seeking "shelter"
||Using Radios And Radio Equipment
TABLE-2: Lightning Safety Education Resources
(as of 20 February 2002)
|National Weather Service
|National Severe Storms Laboratory
|National Lightning Safety Institute
|'USA Today' Newspaper
American Red Cross-Masters of Disaster (Children's Curriculum)
|Kids' Lightning Safety (aka Sabrina's
|National Athletic Trainers' Association
|National Outdoor Leadership School--Backcountry
|University Of Florida (Boating-Lightning
|National Agricultural Safety Database
(Boating-Lightning Protection) www.cdc.gov/niosh/nasd/docs/as04800.html
|Lightning Injury Research (University
of Illinois at Chicago) ttp://www.uic.edu/labs/lightninginjury/
|Lightning Strike and Electric Shock Survivors,
|Global Atmospherics, Inc. (National Lightning