What happens when lightning strikes a lake?

When lightning strikes a body of water, the current travels across the surface rather than penetrating deep into the liquid, similar to the effect when lightning strikes a car or other electrically conductive object. This is called the surface effect and is the principle behind a Faraday cage – a sealed structure that protects the interior from electrical current. When a person is struck by lightning, this same effect occurs, called flashover, which can leave Lichtenberg patterns – complex surface burns – on the skin.

When lightning strikes a lake or ocean, only creatures living near the surface at the time are usually affected by the current. However, it is impossible to determine the exact depth to which each lightning strike will penetrate, so experts warn people not to rely on their scuba diving skills to go swimming during stormy weather.

A bolt of lightning can reach 27,760 degrees Celsius, nearly five times the surface of the Sun. But water is a good conductor of heat, so when lightning strikes water, the heat quickly dissipates. Water will soften the impact of the lightning, so it won’t boil when struck.

Humans often float on the surface of the water, so it is not as safe as fish when swimming in a storm. The electric current from a lightning strike on the water can travel 10-100 meters or more, depending on the intensity of the lightning. Therefore, even if not directly near the lightning strike, swimmers can be damaged by the energy of up to 10 million volts of lightning. To stay safe, people should not go swimming during a storm.