When it’s pelting down and most people have dashed indoors, my father likes to pull on his wellies and clear the ditches around our property. At this time of year the thunder-and-lightning season and this year particularly, this is alarming, especially as he’s 6ft 4in and carries a spade on his mission. His closest shave has been hearing an almighty crack as a telegraph pole yards from his endeavours was hit. Few of us know somebody who has been struck, as the likelihood in the UK is one in three million, but how many of us know what to do when caught in a thunderstorm?

According to experts, the main rules are to avoid open ground and lone trees indeed, people in England have recently been struck in both situations.
A teenager was knocked unconscious while sheltering, on his bicycle, under a tree in a Manchester park. Witnesses saw smoke coming from the boy’s head after a flash and a bang. In Coventry, a man was struck in the open. A passer-by reported that his trousers were shredded and one of his shoes had burnt in half, and a paramedic said most of his body hair was singed.

Rev Christopher Miles, a lightning protection consultant and former electrical engineer for the RAF, says sheltering under a tree is the worst course of action but the most natural. ‘Some boys playing football in Kent were once caught in a thunderstorm, and adults ushered them under a tree,’ he recalls. ‘It was struck, and 17 people were injured. Voltage enters your body from a branch, or, if it travels down the trunk, from the ground.’

This is when ‘step potential’ comes into play. Placing your feet apart increases the difference in voltage across your body and the charge from the ground.Animals’ step potential, with their front and hind feet apart, makes them more susceptible. ‘Curl up in a ball to reduce your height and keep your feet together,’ advises Mr Miles. ‘Shelter under a hedge, or in a wood, where the chance of a tree next to you being struck is small. In mountains, avoid ridges and don’t shelter under overhangs, where there’s danger from different currents in the ground.’

A vehicle provides the best refuge but not because of its rubber tyres. ‘There’s no charge inside a hollow metal structure: the current flows through its “skin” into the ground,’ explains Mr Miles. ‘But don’t fiddle with the radio and or touch any metal.’ Small quantities of metal such as horseshoes present negligible risk. However, metal jewellery can exacerbate burns. According to the UK-based Tornado and Storm Research Organisation (TORRO), since death certificates first recorded demise by lightning in 1852, the number killed by a bolt has fallen from 19 a year to three, although in 1982, 14 people perished, and in 2000 and 2001 for the first time since 1937 nobody did. The overall drop in deaths is chiefly due to medical advances and fewer people working outside.

You’re unlikely to be killed indoors in a developed country. But in the US recently, a man was knocked off a sofa in a basement when lightning struck
a tree nearby, two teenagers playing computer games watched their devices ‘fry’ after a strike channelled through electric wiring, and a man working in his garage was left with an exit wound from his big toe after a current entered him from a sink. Indoors, TORRO advises people to keep away from windows and metalwork and to avoid using the telephone or electrical equipment. ‘If lightning strikes an aerial, the cable may conduct the current into the building where it can jump to wiring or piping.’

An international lightning detection system has long been in place, and the meteorologically minded can set up gadgets at home to monitor thunderstorms, but this year, a new wave of devices is appearing largely aimed at golfers and joggers. Nokia has developed a mobile phone that picks up radio waves from lightning, and a pocket-sized, ‘personal lightning detector’, marketed in the US, sounds an alarm when lightning is nearby. Scout and sports groups can sign up to a service that warns of strikes within six miles of their camp.

But for those reluctant to amass yet more gadgetry, traditional detection methods still work. If your hair stands on end or objects buzz, beware. According to TORRO, lightning may be imminent, as positive charges at the ground strive to unite with a negative charge from above. You can ‘count in’ the storm yourself, too although the ‘one second, one mile’ method is way out, and if you hear thunder, you’re probably in danger already. Count the seconds between flash and clap, divide by five, and you’ll have the distance in miles. So if five seconds elapse, it’s one mile away. If you only count to one, the storm is overhead. In which case, father, if you haven’t run inside already, throw away your spade, roll under a hedge and curl up tight?

What to do in a thunderstorm

If you’re outside

If there’s a building or vehicle nearby, then go indoors or get inside.

If that’s not an option:

Never shelter near or under a lone tree
Keep away from open ground and ridges
Don’t seek refuge under an overhang or in a cave
Shelter, instead, in a wood, avoiding taller trees; in a hollow or dry ditch, or under a hedge, avoiding high points
Crouch down, keeping your feet together, or curl up into a ball
Discard metal equipment, such as golf clubs, guns, spades, bicycles

If you’re inside

Don’t use electrical equipment, including the telephone
Stay away from windows and metalwork, such as pipes and radiators