Look out for mention of thunderstorms in the mountain weather forecasts when you are planning your hill trip, especially after a prolonged period of warm humid days.
While out on the hill you will get a good warning of the potential build up of an electrical storm as they are usually accompanied by the formation of towering clouds which will start to develop as unstable air spirals upwards and condenses.
As a storm approaches, its location can be estimated by noting the difference in time between lightning flashes and the rumble of thunder. The light appears almost simultaneously, while sound travels at a speed of 1 km per 3 seconds. So, a six-second delay means that the storm is about two kilometres away and a nine-second delay means that the storm is about three kilometres away.
Lightning strikes are quite frequent on summits and other projections such as pinnacles, because lightning takes the shortest route to earth.
The advice on this page is informed by the book 'Hillwalking', published by Mountain Training. Illustrations are reproduced with permission.