What does it feel like to be struck by lightning?

Exploding clothing, curious skin marks and the crawling sensation of being covered in ants. Kate Newton meets a man who was struck by lightning and talks to the experts about what happens to your body if you're hit.

Tucked under a large bush on a rainwashed coastal hillside, Martin Williams was watching the sky above Sponge Bay get darker and darker.

He and another fisheries officer had been there for half an hour, concealed in their usual vantage point on a cliff above the bay, with a view of Sponge Bay Island and the rock shelf running between it and the Gisborne coastline.

The area was a hot-spot for shellfish gatherers, who would wait until the tide was low enough to walk right out along the rock shelf to the beds of pāua ringing the island. Poaching was common. It wasn't unusual for Williams and his workmates to nab people with sacks full of hundreds of undersized pāua.

That day in 2014, they were surveilling a group of divers who had headed out in the poor weather - a possible tell-tale sign that they were up to no good.

As drizzle continued to fall, Williams and the other officer, Laura Hansen, were starting to wonder why the divers weren't coming in. The sky beyond the island, over Young Nick's Head, was nearly black and bolts of lightning were coming down there regularly now. Later, Williams heard that more than a thousand lightning strikes hit Gisborne that day. "We were going, 'Wow! That is impressive,' because they were big strikes."

As they waited, one bolt came down in the middle of the bay - "a solid crack, right down into the water".

Finally, the divers came back to shore and started heading up the track. The two men would have to pass the officers' hiding place to reach the car park but Williams, not wanting to linger much longer in the deteriorating weather, suggested to Hansen that they cross over the stile at the head of the track and walk down to meet the men.

The officers and the divers converged on a small ridge about 20 metres past the stile and Williams asked to inspect the catch. He was standing just a little higher than everyone else on the track; a smidgen more exposed.

As he reached down to take the sack from the men, there was an immense, cracking boom and the world exploded with white light. Then came a voice inside Williams' head, slow and warped. It said: you've just been struck by lightning.

Bolts from the blue

Lightning strikes about 190,000 times a year in New Zealand - one strike every 167 seconds, on average. Disappointingly infrequent for Craig Rodger's tastes - a professor of physics at the University of Otago, he has specific research expertise in lightning. "We are low. We are like, a thousand times lower than most of the world," he says. "To give you a feeling, the global average lightning rate is 44 a second. You have to wait three minutes in New Zealand for there to be a lightning strike, on average, and in that time globally there's been about 7500."

In some parts of the world, there are thunderstorms so reliable that they have names. "I've heard of Hector, which is a thunderstorm just off the coast of Darwin," Rodger says. Named by the locals, Hector shows up every evening, and his punctuality is such that storm researchers converge in Darwin to study him.

In New Zealand, the North Island is more lightning-prone than the South Island, but the South Island's west coast gets hit more than any other region of the country, due to spring storms that course their way from the Tasman Sea to the Southern Alps, zapping their way up the mountains.

Lightning is, essentially, a gigantic spark. Inside a thundercloud, huge winds cause pieces of graupel - a kind of soft hail - to swirl round, smashing into each other and knocking tiny bits of electric charge off. Eventually, a huge negative charge builds up in the lower part of the storm clouds: a highly unstable situation. "That charge wants to be grounded, it wants to get cancelled out, so it will leap from the cloud to ground to cancel the charge out," Rodger says. "But in doing so, a huge electrical current flows as the charge flows from the cloud to the ground and we see this as a big electrical spark, which is the lightning flash."

Not all lightning flashes make it to the ground. About three-quarters of all lightning is within clouds or between clouds, Rodger says. "But the stuff we tend to care about is the stuff that involves the ground - where we live."

The most dangerous type of lightning comes from the top of the storm, where the build-up of energy is positively charged (think of the cloud as a giant battery). The danger has nothing to do with the charge itself, but how high up in the storm system it is. "By the time it's going to leap all the way down to the ground you need to have relatively special circumstances and those special circumstances lead to very large currents," Rodger says.

Positively charged lightning strikes are often termed by researchers as 'bolts from the blue' because they travel sideways from the top of the cloud, sometimes grounding many kilometres away from the storm, he says.

"With the negatively charged lightning it tends to be straight down and it's raining, you know there's a thunderstorm, because you're under it. But with the positive lightning it's going sideways and you might not even be aware there's a thunderstorm happening a few kilometres away - you're not being rained on, everything's fine - and then suddenly, bzzzt, this lightning flash arrives really close to you."

Lightning is always on the look-out for the easiest electrical path to flow through to get to ground. "It's looking for high points - so the top of church steeples, power lines, towers." A human, as a living electrical system, creates "a very nice path" for that current to flow through, especially if they're the highest object in the area, Rodger says.

That could explain what happened to Martin Williams as he stood on that small ridge, several kilometres away from the main storm. "If the lightning was about to do that and he suddenly stood up and became the highest high-conductivity line, that would make sense."

Positive lighting - if that's what it was - can carry up to a billion volts and a current of 300,000 amps. How did Williams survive that? "I can only suspect that he wasn't zapped directly - that he was close and so it felt really bad."

'It was like you'd shifted into the twilight zone'

It might have been indirect, but Williams says the immediate sensation that day at Sponge Bay was of a huge, percussive force. "It felt like you'd actually been walloped by something, or you were inside a bass speaker."

As the bolt struck, there was a millisecond flash of intense, burning heat, that had already dissipated by the time his brain could even register it. But the strangest sensation, as he stood on that coastal ridgeline - somehow, he'd held his ground - was a sense that time had dilated and the whole world had dimmed. "It was like someone actually turned down the brilliance on your TV... It was like you'd shifted into the twilight zone."

In that slowed-down, suddenly silent world, Williams' realisation that he'd been hit by lightning was followed immediately by another: "I'm still alive." Then the world came back with a rush. "Suddenly time caught up and you just felt like a tingling, like pins and needles throughout your whole body - it actually felt like you had ants crawling all over you."

He realised his workmate, Laura Hansen, had also been hit, but the strike had missed most of her body, clipping her round the head as she threw herself to the ground. "I was going, "Laura! Shivers! We got struck by lightning, we're alive!" She wasn't too happy - I think she probably took it a bit more seriously than I did." The divers, standing slightly lower on the track, were untouched but in disbelief at what they'd just seen.

Williams managed to discharge most of the static electricity still fizzing through his body by walking down to the wire fence next to the stile and grabbing hold of it. But the buzz - a combination of adrenalin and the electric charge - lasted all afternoon.

He and Hansen considered getting checked out at the hospital, but by the time they'd inspected the divers' catch - turned out, it was entirely legal - and driven back to the office, the worst of the static had subsided and they didn't seem to have sustained any injuries.

Williams has his own theory as to why the pair survived nearly unscathed. "When we look back on it, when you go to that Sponge Bay area there's a metal rail that runs along the car park area. And I think what happened is the bolt of lightning was going directly to where the metal rail was. As I leant over and stood up, I interrupted the flow of lightning as it was going towards the car park area."

He believes that metal rail saved his life. "If I'd got a direct hit, I'd have been absolutely fried."

Cows, Cubans and currents

People do get "absolutely fried" - although ACC figures suggest injuries in New Zealand are both rare and not usually serious. In the last three years, only 13 ACC claims have been made for lightning injuries, at a total treatment cost of about $1700.

Last December, a lightning bolt from a huge electrical storm struck rugby posts at Hamilton North School, travelled through the ground and hit a school building, giving four teachers a shock that landed them in hospital with similar sensations and symptoms to Martin Williams.

Less lucky were four cows killed by another lightning strike in the same storm. The physiology of cows - and the fact most of them live outside in New Zealand - makes them comparatively more prone to lightning shocks than people, Craig Rodger says.

When lightning hits the earth, it momentarily creates a huge electric field, with voltage spread across the ground for hundreds of metres. "They say the safe thing to do as a human being if you're out and there's going to be a lightning flash somewhere near to you, is to put your two feet close together. Then there's very little voltage difference between your feet, and so only a very small current will flow."

Cows, however, being "big long creatures", have about a metre or so between their two sets of legs. "That means that there's quite a significant voltage difference between the forelegs and the back legs of the cow, and so a current will flow through the cow's body, through the heart and quite possibly disrupt it and stop it."

In lightning-prone parts of the world, the phenomenon is a known and real occupational hazard. The most commonly struck group of people in the world are Cuban agricultural workers. "Cuba is a lightning hotspot," Rodger says. "Then there's lots of agricultural workers who are working outside. Put that combination together, and then I'm imagining rakes and hoes and things being waved round, and you've got problems."

Golfers in Florida are next in line: Florida has disproportionate shares of both lightning strikes and retirees - put them together and you have an army of people walking around with makeshift lightning rods in their hands.

"It can explode your clothes from your body"

At its most lethal, a direct lightning strike can trigger cardiac arrest. An emergency medicine specialist at Waikato Hospital, John Bonning, says three-quarters of people who are directly hit will go into cardiac arrest, and 10 percent will die. "And 100 percent [who survive] will lose consciousness and not have much recollection." Indirect hits, or side strikes via the ground or nearby structures, can result in a spectrum of injuries or symptoms, but few of them cause lasting damage.

One of the first things emergency doctors treating suspected strike victims look for are skin markings. Sometimes these are small entry and exit burn marks, but in about one in five cases, a very unusual symptom occurs. The energy of the strike can prompt electromagnetic interactions with skin moisture (sweat or rain), creating peculiar red, raised patterns on the patient's body. Known as Lichtenberg figures, they look like spreading ferns, or actually, complex fork lightning - a weird physical onomatopoeia.

It can get even weirder, Dr Bonning says. "This is another very unusual statistic, which I have never seen but is described, [which is] that the steam created by evaporating sweat or water on your body can, in fact, explode your clothes from your body."

Presuming a lightning strike victim survives, there can be some other more lasting effects. Ruptured ear drums and tinnitus - either temporary or permanent - are common. About 15 percent of direct strikes result in dislocated shoulders from the immense jolt of electricity, similar to what can happen when someone gets tasered, Dr Bonning says. "That immediate, complete contraction of every muscle in your body because of this massive amount of electricity that's gone through you just physically jolts the shoulder out of joint."

Sensitive organs, such as the pancreas and eyes, also don't respond terribly well to large volumes of electricity coursing through them either, Dr Bonning says. "[Strike victims] can develop cataracts in up to 10 percent of lightning strikes... This intense electrical voltage that goes through the body can just cause a variety of different complications and the lens is just one of these sensitive organs."

Other temporary symptoms can look like stroke injuries. "Their arm might be numb, they may not be able to walk, may not be able to talk, they can be stunned, they can have confusion, often amnesia."

While those symptoms will quickly subside, Dr Bonning says lightning strike victims can underestimate the psychological effects. "Particularly if it's a significant strike ... that is something you would really want to look at somebody for psychological follow-up and support."

Often though, the only damage is some achy muscles. "You probably will, the next day, feel really quite sore."

On a summer day in 2019, Martin Williams is back on the cliff edge above Sponge Bay, trying to pinpoint the exact spot where lightning struck five years beforehand. The water below is peacock blue and the sun is so bright it forces your eyes closed. Not even the most benign of clouds marks the sky. "Here," he says. He mimes how he reached down to take the bag of pāua from the divers.

Ask Williams if he ever noticed side effects from that stormy day and he just gestures to his bald head. "All my hair fell out." Only joking, he adds. A Lotto ticket he bought immediately afterwards didn't win a cent. "My near-death experiences don't come out with financial gains."

The one lingering effect, if it counts, is a much more circumspect attitude to big weather. "If I see any sign of a thunderstorm, I'm not out there - I'm not going to do that again."