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Knowing the risks: lightning

Lightning strikes are common, but deaths caused by lightning in the Scottish mountains are not. However, even though the incidents are few, the prudent mountain-goer should take heed of the advice on this page. In recent history there have been two recorded lightning strike deaths in the Scottish mountains: one on Ben Oss in May 2004 and another on Na Gruagaichean in June 2019.

Plan ahead

Check out the mountain specific weather forecasts prior to heading out on the hill.  If thunderstorms are forecast, then change your route plan either to a different area or a lower level route – or perhaps plan an earlier start so you are down off the high ground before the thunderstorm is predicted.

Most of us are not meteorological experts, but we do spend a good deal of time in the mountains. So even if a thunderstorm is not forecast, keep an eye out for those developing cumulonimbus clouds, particularly on a warm summer’s afternoon. Surprisingly, thunderstorms are also common in winter, especially in unstable west or north-westerly airstreams.

Cumulonimbus clouds can develop rapidly and are the type that produce thunderstorms. Photo courtesy of the Met Office.

If caught out, what are your options?

  • Your distance from a thunderstorm can be estimated by measuring the time between seeing the lightning flash and hearing the thunder. The length of this interval in seconds can be divided by three to give an approximate distance in kilometres.  E.g. 6 seconds between the lightning and thunder would suggest the storm is 2km from you.  Monitor this timing to assess if the storm is approaching you or heading away.

  • The calculation above is a useful guideline BUT it is important to realise that if you hear thunder, you are already within range of where the next strike may occur – lightning can strike as far as 14 km away from the storm. In addition, on windy days the sound may be muffled, or you may not be able to hear the thunder over the wind noise, so be vigilant for any lightning flashes.

  • The threat of lightning continues for much longer than many people realise. After the storms move away and you stop hearing thunder wait at least 30 minutes before assuming it is safe.

  • If you hear thunder it is vital to get down off high ground immediately.  Lightning will take the shortest route to earth, so if you are the highest point in the immediate vicinity drop down off the summit, exposed ridge line etc if it is safe to do so.

  • Regardless of where you are outside, even on lower ground, there is no safe place from lightning.  To minimise the chances of a strike you need to become a small, round target. Your best option is to put extra clothing and waterproofs on, seek the lowest point possible and sit on your rucksack with your knees drawn up to your body. Or squat close to the ground, with hands on knees and with head tucked between them. Try to touch as little of the ground with your body as possible; do not lie down on the ground. If you feel your hair stand on end, drop to the above position immediately.

  • Make sure that you place any items such as poles, ice axes, crampons and climbing hardware well away from you until the storm has passed.

  • If any of your equipment is ‘buzzing,’ move away from it immediately. Another feature is the emission of a blue glow to the buzzing equipment. This is a phenomenon known as St. Elmo’s fire and can indicate that a strike is likely to be imminent.

  • Sheltering under a rock overhang or in a cave is hazardous because a lightning strike will bridge the gap between the rock above you and the ground below. 

  • Trees are uncommon above 600 metres in Scotland’s mountains, but in the unlikely event that there is one, don’t be tempted to shelter underneath it for the same reasons as above.

  • Move away from each other if you are in a group; then if the worst occurs it is likely that there will be others to help.

  • Do not position yourself next to a burn, lochan or wet/boggy ground; water will conduct electricity

Find out more

The Met Office has some excellent information and videos to further expand your knowledge on this potentially dangerous weather phenomenon.

www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/thunder-and-lightning

www.metoffice.gov.uk/weather/warnings-and-advice/seasonal-advice/health-wellbeing/stay-safe-in-thunder-and-lightning

This page was produced with kind support from John Mitchell, Met Office, Aberdeen.