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Thunder and Lightning

Swimming in the rain is fun but swimming in a thunderstorm is stupid. We share what to do if you get caught in a thunderstorm to minimise the risk of being struck.

When a Thunderstorm Approaches

A thunderstorm is an impressive natural spectacle and you don't need to be afraid of it. The prerequisite for being able to enjoy it is a safe place to stay. This sight is safest from a distance.

Before planning your swimming trip, you should take a look at the weather forecast. If thunderstorms are forecast, it is better not to go swimming that day.

Observe your surroundings, even if you are relaxing in a lake or swimming pool. A thunderstorm does not suddenly appear in the blue sky. You will first see thick clouds of cauliflower that are darkening. The wind is picking up. The risk of a thunderstorm is particularly high in humid and warm temperatures.

At the latest when you notice the first lightning, stop swimming and move well away from the water surface. Lightning often strikes raised points. Your head on the surface of the water is one of them. You don't need to unnecessarily increase your risk.

Swimming in indoor pools is generally harmless, as the construction of the building must have adequate lightning protection equipment. But expect that the pool attendant will ask you to leave the water. Outdoor pools must be closed and evacuated if a lightning strike has been identified within 10 km of their location. This is not a chicane, it is only for your protection.

If you swim in the outdoor area of a swimming pool, leave the pool immediately in the event of a thunderstorm. Refrain from swimming into the indoor pools through one of the frequently available connecting channels. Water conducts and in the event of a lightning strike, the dangerous voltage reaches you there too.

Be Smart About Lightning

Lightning is one of the most dangerous aspects of hiking or camping in the rain. If you're swimming or in a boat, get out of the water immediately. If you're on land, find a spot that's not on or near the highest geographical point.

The most dangerous element of lightning is its unpredictable behavior. It can strike before, during and after the main thunder clouds have passed overhead. No one can pinpoint with certainty when and where lightning will strike next.

Lightning will typically strike within a 10-mile radius of its parent thunderstorm, with an emphasis on the word typically. It has been reported to strike as far away as 50 miles from its parent thunderstorm source. That's quite the distance to keep track of as a swimmer.

The only hint that we are given as swimmers is that rain typically precedes lightning in most cases, but even that’s not a hard and fast rule. For this reason, it’s generally advised to stop swimming when heavy rains ensue, or thunderstorms are looming on the horizon.

When you see nearby lightning, exit the water and get to shelter immediately. In this scenario, you definitely don’t want to risk getting back to land too late, as lightning can contact large bodies of water. Since water conducts electricity, being caught in the wrong place at the wrong time could have lethal consequences. Swimming and thunderstorms just don't go together.

Each year lightning claims many lives or causes injuries. Up to 80% of those injuries happen when people use telephones during thunderstorms and receive an electric shock, hearing damage, or burns when lightning strikes telephone wires in their area. This is obviously the largest source of lightning related injuries.

Keep in mind that storms can be extremely frightening for children, so if you're camping with kids, plan ahead with topics that will keep your kids calm during dangerous weather.

Warning Signs

First long term warning signs are obviously the build up of storm clouds. This may be evident several hours prior to arrival of the thunderstorm, so it is worthwhile being aware of the surrounding weather to avoid being in a high risk location when the storm arrives.

Short term warning signs are the familiar sights and sounds of lightning and thunder. The time difference between the lightning flash and the sound of the thunder can be used to estimate the distance to the lightning strike/storm. When there is a 10 second gap between the lightning and the thunder, the lightning is about 3 kilometres away. At 3 seconds it is about 1 kilometre away. When the time difference is less than 10 seconds (lightning less then 3 kilometres away) it is time to seek shelter urgently!

These signs may precede a lightning strike:

  • A build up of static electricity like hair standing on end.

  • "Buzzing" from nearby rocks, fences, and such.

  • At night, a blue glow may show from an object that is about to be struck.

If you notice any of these signs, MOVE IMMEDIATELY!

First Aid

If someone has been struck be lightning, apply immediate Expired Air Resuscitation (EAR) if not breathing, or immediate Cardiopulmonary Resuscitation (CPR) if no pulse. Continue this until medical help arrives and they will have a good chance of survival. You will not receive a shock from the victim.

How Lightning Strikes

Lightning (ground strike) occurs when the charge of static electricity in the clouds builds up to the point where there is enough voltage for a spark to jump the gap from cloud to earth.

The charge in the cloud will be opposite to the corresponding charge induced on the ground. These opposite charges are attracted, and will try to cancel each other out through the lightning strike.

High points, spikes and conductors will each affect the electric field, usually concentrating it. This means that tall, pointy or conductive objects are more likely to be struck by lightning than other objects.

A Miss Could Still be a Hit!

Just before a lightning strike, the voltage (potential difference) between the cloud and the ground can be several million volts! The charge on the cloud and on the ground is dispersed over a relatively large area.

When the lightning strikes, the lightning bolt is actually a track of ionised molecules in the air. The average lightning bolt carries a current of 10,000 to 30,000 amps, but only for a very short time.

All this current must move from being dispersed over the ground (or cloud) to/from the lightning bolt, so large currents and voltages occur in the ground. The voltage is very high near the strike, and low away from it. This causes "step potential".

Step Potential

Step potential means that if someone touches the ground at two points, one closer to the lightning strike than the other, an electric current will flow through them.

The closer the lightning strike, or the wider the step between the two points, the higher the step potential, the higher the current, and the more serious the injuries.

So even if you are not directly hit by lightning, just being close by can result in electrocution. Therefore, take good care to avoid the step potential.

Facts and Myths

Only about 30% of people struck actually die, and the incidence of long term disability is low, particularly when first aid is applied promptly.

When struck, people do not glow or "fry to a crisp", but the heart and breathing are often affected.

Lightning can and does strike in the same place more than once!

Worldwide, thunderstorms are producing approximately 6,000 lightning strikes every minute!

Do This


When a thunderstorm comes, seek shelter immediately, ideally in a house or other permanent structure.

Cars protect you in a thunderstorm because they conduct voltage around you like a cage without danger. This principle is called a "Faraday Cage" and also applies to railway wagons and similar constructions. If driving, slow down or park away from trees, power lines, and such. A shed or tent is not safe enough and do not shelter beneath a tree.

Get Out

If swimming or surfing leave the water immediately. When lightning strikes the water the ekectricity runs along the surface and can hit you.


If boating, go ashore to shelter as soon as possible. A bridge or high jetty may offer immediate protection. Be sure the mast and stays of a sailing boat are adequately "grounded" to the water.

Get Wet

Let your outer clothes get wet in the rain to conduct any electricty away from your body. If your clothes are wet, you are less likely to be seriously injured if struck, as most of the charge will conduct along the outside of your wet clothes rather than your body. Put your hood up so it gets wet in the rain and protects your head by keeping it dry. If possible, keep your inner clothes dry for insulation. A poncho might help.

Turn into a Ball

If there really is no shelter at all, find a low place, preferably in a hollow. Assume the crash position as shown on airplanes, with your head between your legs, crouch alone with feet together to avoid too much contact with the earth. This will keep you as low as possible without creating a step potential risk. Remove metal objects from your head and body. Cover up in a large rain cape or poncho.

Wait until the storm clears

It is also important not to leave your shelter too early. There is still a danger up to half an hour after the thunderstorm is over, and yes, lightning can strike the same place, or the same person, twice.

Do NOT Do This

Never shelter under a single tree or a small group of trees. As the highest point in that area, the tree is likely to be struck. Being near the tree increases the risk of step potential.

Don't seek shelter under a tree. There is an exception if you are in the middle of a forest with trees of the same height. There the thunderstorm is looking for other destinations. But even there, stand in such a way that your legs stay close together.

Don't hunker down beneath large branches that could break and fall during a storm.

Don't sit in small structures or fabric tents because they lack sufficient mass to conduct a lightning strike safely around you. Depending on the method of construction they may even attract lightning.

Don't be the highest object.

Don't shelter beneath tall things.

Don't stand near metal poles, fences, clothes lines, etc.

Don't fly kites or model aeroplanes with control wires.

Don't handle fishing rods, umbrellas or golf clubs, etc.

Don't touch any metal parts.

Don't ride horses, cycles or drive in open vehicles.

Don't lie down because of step potential.

Man Escapes Lightning Bolt Death in Wet Clothes

30 Jun 2008, by Mike Baron

When your clothes are wet, you are less likely to be seriously injured when struck, as most of the charge will conduct through the surface of the wet clothes rather than your body.

A Minnesota man by the name of Kent Lilyerd was out in his backyard during a thunderstorm attempting to protect his gazebo from flying away, when he was struck by powerful lightning.

Kent Lilyerd, who was wearing a baseball cap with metal buttons, was wrestling with his gazebo when lightning struck one of the buttons on his hat.

The lightning struck his head and travelled through his wet clothes, re-entering through his steel-toed boots. Doctors say if it wasn't for his wet clothes, he'd probably be dead (head-to-toe strikes are the most dangerous).

Kent claims he knew right away that he was struck by lightning: "I knew right away what it was when I smelled it," the welder said. Kent has been shocked a few times due to his line of work, but claims those shocks don't even come close to the shock he got from the bolt.

The nickel in Kent's pocket was blackened after the strike and the bullet in his pocket melted. He could also smell his burnt hair. On a scale from 1-10 in pain, Kent says it's been an 11.

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