Myths and risks

Lightning myths about being struck by lightning

Carrying or wearing small metal objects (e.g. necklace, bracelet, ring, earrings, body piercing stud, belt buckle, underwired bra, keys) does NOT make that person more likely to be struck. Rather, the objects may cause burns, sometimes in the shape of the object, on those parts of the body they are in close contact with because the metal heats up rapidly to very high temperatures. Very thin metal objects, such as a necklace, may even be vapourised.

Metallic and plastic mobile phones and smartphones do NOT attract lightning and nor do the electromagnetic waves used for communication. However, wearing ear phones or placing the mobile phone against the ear may result in burns around the ear and cheek if that person is struck. Some, but not all, researchers suggest they may disrupt the flashover effect and lead to some of the electric current entering the head and causing more serious injuries. However, such a possibility should not stop someone carrying a smartphone to use in case of an emergency such as calling for medical assistance.

Someone who is struck by lightning does NOT retain an electric charge, unlike someone in contact with a live electric circuit. Emergency medical help should be summoned as soon as possible. If the person is in cardiopulmonary arrest then cardiopulmonary resuscitation (CPR) should be attempted and continued until paramedics arrive with a defibrillator. Also a public access defibrillator may be available nearby which is safe and simple for a lay person to use. Nearly ten thousand AEDs (Automated External Defibrillators) have been placed in community centres, schools, shopping centres, railways stations, local government offices, gyms and workplaces around the UK. When turned on, most of these computerised life-saving units have spoken prompts, and some may have visual displays to instruct the user. Act to save a life – every second counts. Look for these and similar signs in or on the wall outside buildings:
More details on defibrillators at Community Heartbeat.

Outdoor risks of being struck, and safety advice

Too often people put themselves at risk by being caught out during a thunderstorm in a wide open and exposed location such as on a hill, mountain, moor, cliff top, beach, lake and sea.

Safe shelter from a lightning strike can be found in a sturdy, well-grounded and enclosed building or a fully-enclosed metal-topped motor vehicle but they may be some distance away when thunderstorms threaten. Thunderstorms are dangerous so have a lightning safety plan. Know where you will go for safety and how much time it will take to get there. Check the weather forecasts in advance of a planned visit to, say, en exposed location such as a hill or mountain and reschedule if there is a risk of a thunderstorm. Avoid being caught out on the wide open spaces of a golf course or sports fields when lightning threatens.

Get to the shore and away from lakes, sea and other bodies of water where you would otherwise be the highest object in the vicinity. Kayaks, jet skis and small boats with no cabins are unsafe locations. Seek shelter onshore inside a well-grounded substantial building or a metal-topped enclosed vehicle. Large boats with cabins, especially those fitted with lightning protection systems, are relatively safe but stay inside the cabin and away from metal surfaces.

Be aware that no place outside is safe when thunderstorms are in the area. If you hear thunder, lightning is close enough to strike you.

Do NOT seek shelter under a tree. Sheltering under a tall tree from the heavy rain of a thunderstorm is dangerous during a thunderstorm. If lightning strikes a tree then the electric current passes down the trunk and may side flash (splash) to the person standing next to it as the human body is a better conducting pathway to the ground.

Do NOT shelter in huts, sheds, park shelters and bus shelters. They are dangerous as these small buildings are often not electrically grounded. Occupants may experience serious, even fatal, electric shocks if lightning strikes them.

Check out the extensive US National Weather Service Lightning safety website and the lightning safety page of the Royal Society for the Prevention of Accidents.

Reminders of when to seek shelter from lightning

There are many rhymes that remind us what to do to keep us safe from lightning such as 'When thunder roars, go indoors'.

The distance of lightning can be estimated using the 'flash-to-bang method'. Light travels faster than sound so we see lightning first before hearing the thunder. Count the number of seconds between seeing the lightning and hearing the thunder and then divide by three to give the distance in kilometres or divide by five to give the distance in miles.

The 30-30 rule has been widely adopted to know when lightning poses a serious threat. People are advised to seek shelter if thunder is heard within 30 seconds of seeing the lightning flash. A time of 30 seconds or less from 'flash-to-bang' indicates that lightning is dangerously close – within 10 km or 6 miles. The other part of the 30-30 rule is to wait 30 minutes from the last lightning flash and thunder before resuming outdoor activities:

'Half an Hour since Thunder roars, now it's safe to go outdoors'

Lightning risk on mountains

One of the most dangerous places to be when lightning threatens is on an exposed mountain, ridge or hill. If thunderstorms are forecast, don't go walking in these places, reschedule your visit. Even if the weather forecast is good it is important to keep a lookout for unexpected bad weather. If you suspect a thunderstorm is approaching, move downwards rapidly but safely. If possible choose a route down that does not follow a ridge or other exposed route. If the storm overtakes you, it is a question of judgement whether you keep moving down to a safer place (metal-topped, enclosed vehicle or well-grounded, substantial building), or stop and make yourself small. Don't take shelter in cracks, overhangs or small caves: lightning will often follow this route to earth. Sheltering under a tree is dangerous too.

If you cannot get to a safe location, seek the lowest ground around, away from trees or lakes. Make yourself as small as possible by crouching down or sitting upright with your head tucked down, knees drawn up and hands on your knees. Do not lay flat on the ground as this may increase the electric shock you receive from a ground current if lightning strikes nearby.

Further advice on Mountaineering Scotland.

Indoor risks from lightning

Half of the known incidents in which someone experienced an electric shock from lightning in the UK happened indoors when lightning struck the building they were in. Of the indoor incidents during the past 25 years, around one quarter of people who suffered an electric shock were using a corded (landline) telephone. Others were standing near an external door or window or were near or touching electrical equipment or metal objects connected to the plumbing circuit (radiator, kitchen sink, bath and shower).

If someone experiences an electric shock indoors when lightning strikes the building, usually it has much less serious consequences than electric shocks from lightning outdoors. This is because telephone lines (providing an entry point into a building for electric current from the lightning) and electrical equipment inside the building have surge protection devices to reduce excessive voltages. No deaths inside well-grounded, substantial buildings have been reported in the past 25 years in the UK although they were not uncommon a century ago when buildings lacked electric wiring and plumbing pipes inside the walls and were not well-grounded electrically. Nevertheless, there have been some serious injuries from lightning indoors in the UK in the past 25 years so be cautious and avoid contact with corded telephones and metal objects connected to the electricity and plumbing circuits.

People struck while using a corded (landline) telephone experience an electrical and acoustic shock: they often hear a loud bang or click. They may be thrown across the room and thrown to the ground as their muscles experience a violent reaction to the electrical shock. They may be knocked unconscious briefly and suffer temporary loss of hearing and burns to the face or upper body. Problems to the eyes or ears may continue for months or even years. Most common is for cataracts to form several months or even a year or so later. Using cordless mobile phones, smartphones, computers, laptaps and tablets indoors is generally safe.

Small structures that provide shelter from the rain in gardens, allotments, parks, on mountains and golf courses, or when waiting for a bus are dangerous places to be inside when lightning strikes them. They are not electrically grounded so lightning may not pass around the occupants but may strike them inside through the roof or an open side.

One of worst UK lightning tragedies took place in a park shelter on 21 August 1939 in Valentines Park, Ilford. Twenty eight people had taken shelter there when their picnics were disrupted by a thunderstorm. Five adults and two children were killed and 21 others were injured.

Routes by which someone is struck by lightning

Not everyone struck by lightning experiences a direct strike.
There are many routes and mechanisms by which someone may be struck.
A direct strike may account for a relatively small proportion of injuries and fatalities as shown below (the percentages may vary from study to study):

Source: Environment Canada
Electric shocks from lightning can occur when someone is outdoors and in contact with an object that is struck by lightning such as a metal gate, fence, tree, umbrella, golf club, fishing rod or even another person, or indoors touching an object that is part of the conducting route (electrical and plumbing circuits) for the lightning discharge to reach the ground when it strikes the building.

When an object is struck by lightning, the electric current may side flash or splash from the object to a person nearby as the human body is a better conducting route to earth than the object initially struck.
Side flashes commonly involve a tall tree. A 20 to 30 metre tree is a strong contender to provide the initial attachment to the downward stepped leader of a lightning strike in a relatively open location such as a park, golf course or farmland if lightning was going to strike in the general vicinity. Lightning will flow down the tree and jump to the person standing nearby.
In contrast, holding an umbrella, golf club or fishing rod in an open location offers a much smaller attachment radius for the stepped leader than a tall tree.
Only if lightning was about to strike anyway within, say, 2 to 3 metres of the person holding such an object would the object be the preferential attachment point rather than the point on the ground the downward leader was heading for.

When lightning strikes an object or the ground, the electrical current spreads outward from the strike point rather like ripples spreading out from a pebble dropped in a pond. Someone standing across these ripples experiences an electrical current up one leg and down the other as the human body offers less resistance for the current to pass than the ground. This is called the step voltage effect or ground current.
Leg muscles spasm violently and a person is thrown off their feet. Victims may not be able to stand as they continue to experience numbness or paralysis in their legs for minutes or even hours later. Entire sports teams have been knocked over by the step voltage effect. The wider apart the feet, the greater the induced electrical current passing through the body which explains why sheep, cows and horses are often killed by this effect.

Also if within around 20 metres of a lightning strike, instead of the ground current spreading out relatively uniformly from a strike point as a ground current, the electric current may take the form of ground surface arcing, when the lightning flashes along the ground surface in the form of a star burst of flashes. Ground surface arcs carry more current than the areas in between so if a person experiences one of these bursts then the effects may be much more serious.

Unconnected upward leaders or streamers.
Overlying thunderstorms attract upward streamers from objects at the ground, one or more of which may connect with the downward stepped leader to create a cloud-to-ground lightning flash. Many upward streamers fail to make contact but the electric current of an upward streamer originating from a person may be intense enough to cause them injuries. Signs of an upward streamer include a person's hair standing on end and for metal objects being worn or carried and nearby rocks to buzz or crackle.

The shock or pressure wave from a nearby lightning strike may give rise to blunt trauma injuries.

Non-electrical ways of being injured by lightning

Lightning may cause injuries through various non-electrical effects:
  1. sudden explosive expansion of the air around the lightning channel. The pressure or shock wave may throw a person violently to the ground causing injuries;
  2. intense magnetic fields generated around the channel by the very high electrical currents present. These may induce large but short-lived electric currents in a body causing the heart to stop or to go into rapid ventricular fibrillation causing death with no marks on a body. Researchers have suggested that healthy young climbers and hikers found dead with no visible evidence of being struck by lightning may have been killed by this effect.
Indirect effects of lightning include:
  1. injuries through being struck by falling roof tiles and masonry when lightning damages a building;
  2. fires initiated by lightning discharges due to overheating of electrical circuits and appliances in buildings. This may result in the occupants suffering burns and the effects of smoke inhalation;
  3. lightning striking near a motor vehicle, especially at night, may temporarily blind the driver causing them to lose control of the vehicle and crash; farm animals stampeding if frightened by thunder and lightning and resulting in the trampling of people nearby. A rider may be thrown if their horse is startled;
  4. Lightning hitting a tree may instantly vapourise sap, causing strips of bark and branches to be ejected explosively. These may strike people nearby, causing injury or even death.

Lightning books: further reading

In Lightning: Nature and Culture (Reaktion Books, London, 2015) Professor Derek M. Elsom explores the subject of lightning in relation to its characteristics and different forms, improvements in scientific understanding, its impacts, ways to reduce the risks it poses to people and activities, and how lightning is embedded in our culture from myths, folklore and legends to art and design:
Reaktion Books
University of Chicago Press

Other key books about lightning, lightning injuries and lightning safety include:

Andrews, Christopher, Mary Ann Cooper, Mat Darveniza and David Mackerras, Lightning Injuries: Electrical, Medical and Legal Aspects (Boca Raton, 1992)

Bouquegneau, Christian and Vladimir Rakov, How Dangerous is Lightning? (New York, 2010)

Rakov, Vladimir A. and Martin A. Uman, Lightning: Physics and Effects (New York, 2003)

Smith, Craig B., Lightning: Fire from the Sky (Newport Beach, 2008)

Uman, Martin A., All About Lightning (New York, 1986). This edition is an unabridged and corrected publication of Martin Uman's Understanding Lightning (Pennsylvania, 1971)

Uman, Martin A., The Art and Science of Lightning Protection. (Cambridge and New York, 2008)