So where did this rumor come from? Xiaomi points out that when people used “old-fashioned” wired telephones, there was concern about lightning being conducted by the wires. People have been killed when using their wired phone during a thunderstorm. In one example, a New Jersey teen was killed back in 1985 when lightning caused an electrical surge to run through his telephone wire. The electricity entered his ear and led his heart to stop.
But as it turns out, the majority of lightning consists of low-frequency electricity while smartphones use high-frequency electricity. This means that the probability of lightning affecting signals from your smartphone is “relatively low.”
The National Weather Service says that you have a 1-in-15,300 chance of getting struck by lightning over the course of your lifetime
But if you happen to be inside and are using your mobile phone, a thunderstorm will have no affect on how well the device sends and receives signals.