Your mobile phone doesn't attract lightning: expert debunks the myth and explains how to stay safe during a storm

Lightning protection expert Jiří Kutáč has debunked the widespread belief that a mobile phone in your pocket can attract lightning during a storm, and offered advice on how to behave properly, both outdoors and at home, to avoid being struck.

According to him, the weak radio waves emitted and received by a phone have absolutely no effect on the path a lightning bolt takes. "No, definitely not," the expert says when asked whether a gadget in your pocket poses any danger. While a phone does contain metal components, there's simply too little metal for it to make any difference.

The main piece of advice for anyone heading out on a hike is to keep an eye on storm activity. If only 30 seconds pass between a lightning flash and the sound of thunder, it's time to find solid shelter — a stone building or a viaduct, but never a tall tree. The risk of being struck is higher at the edge of a forest, while it decreases deeper inside the woods.

If there's nowhere to take cover, you should make yourself as low to the ground as possible: crouch down, wrap your arms around your knees, and keep your heels together. The danger isn't just a direct strike — being near the point of impact is risky too, since the current spreads out from the strike point in concentric circles at varying voltage levels, creating what's known as step voltage. Kutáč notes that a discharge can travel through the soil for up to a hundred meters.

The most dangerous thing you can do during a storm is lie flat on the ground. "If we lie down, the conductive path runs straight through the heart, which can be fatal," the expert warns. Conductive items like trekking poles or bicycles should be set aside at least three meters away from you.

A car with a metal body is considered safe shelter — it works like a Faraday cage. If lightning strikes the vehicle, the charge travels along the outer metal surface of the body and discharges into the ground through the wet tires. However, it's important to keep all windows closed, avoid touching any metal parts inside the car, and not use the radio or charging devices. This protection doesn't apply to convertibles with fabric roofs, for example.

The expert also addressed children's summer camps specifically: parents should ask camp counselors in advance what precautions are in place in case of a storm. Portable detectors are used to monitor charge buildup in clouds — festivals and sports event organizers rely on them, and camps may use them too. Tents should be spaced more than three meters apart to avoid parallel current exposure, and areas where people gather should ideally be protected by a system of interconnected metal grounding loops around the site. Lightning can also mechanically damage trees to the point of causing them to fall, which is another risk to keep in mind.

The most recent incident of this kind occurred in early July near Jindřichův Hradec, where a lightning strike injured six people.

The expert emphasized that being indoors doesn't automatically guarantee safety either. During a storm, you shouldn't take a shower, wash dishes, or use power tools — if lightning strikes a building or nearby, the discharge can travel through the plumbing and electrical wiring into an apartment.

In the city, among tall buildings and streetlights, a person is generally within their protective zone, but the three-meter rule still applies here as well. "People often take shelter from a storm right at building entrances, but conductive down-conductors running from the roof pass within three meters of there, and that needs to be taken into account. If lightning strikes the building, that down-conductor behaves just like a tree, and the lightning current could injure us," the specialist warns.

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By the Around Prague newsroom