Thunder and lightning


Thunder and lightning is a potential hazard which should be taken seriously when walking outdoors. It’s wise to familiarise yourself with what to do if you encounter a thunderstorm. 

Direct lightning strikes are rare.  Partial strikes are more common, either through induction from a nearby object or from the ground. Reducing surface contact with the ground or object will reduce the power of the strike.

Here are some safety tips to reduce the risks:

  • Plan ahead.  Always check the weather forecast before starting a walk.  We recommend checking the Met Office and Mountain Weather Information Service. If storms are forecast, consider cancelling the walk or altering the route to one at a lower elevation, or on less exposed ground. Be especially cautious after a prolonged period of high humidity.
  • Monitor the weather. Weather forecasts are mainly accurate, but they can’t always predict the exact time and location of storms. Keep an eye on the build-up of clouds – if they start to become menacing, it’s time to review your plans. On warm days the danger will increase during the day as the heat builds.
  • Be aware.  As a storm approaches, its distance can be estimated by measuring the time between lightning flashes and the rumble of thunder. Lighting appears almost simultaneously, while thunder travels at 1 km per 3 seconds. So, a three-second delay between lightning and thunder means that the storm is about 1 km away; a six-second delay means that the storm is about 2 km away.
  • Lose height first. If you get caught by an approaching storm, try to put higher ground between you and the storm. Lightning strikes are more frequent on summits and other projections because lightning takes the shortest route to earth. The higher and more exposed you are, the greater the danger. Only descend if it’s safe to do so; scrambling quickly on uneven terrain can be particularly hazardous in rainfall.
  • Find a safe place. It’s safest to find the lowest open ground rather than taking shelter in caves or under trees - these will put you at risk if struck by lightning, as the lightning takes the quickest route to the ground. Ideally crouch or sit on the ground and aim to ensure that there is higher ground above you.
  • Minimise contact with the ground and any conducting objects. Ideally crouch or sit upright on top of insulating material such as rucksacks or sleeping mats, with hands on knees rather than touching the ground. Although they don’t significantly increase the risk of attracting a strike, it’s wise to lay metal items aside until the storm passes e.g. tools or walking poles. Avoid metal fences. If in a group, try to space out slightly.
  • Help others. It is safe to touch someone who has been struck by lightning and provide them with CPR and First Aid. Anyone struck by lightning should always seek medical advice.