Lightning is an electrical discharge that happens when a region of a cloud acquires enough electrical charge to break down the electrical resistance of air. They can occur within a cloud, between clouds, or between a cloud and the ground, carrying tremendous amounts of energy that ignites the surrounding air into a 30,000 Cº plasma and produces a bright flash and a shockwave that we hear as thunder 1,2.
Considering its dangerous nature and very conspicuous manifestation, it is no surprise that lightning has frightened and fascinated humans since ancient times, as evidenced by its widespread representation in art, myths, and other aspects of human culture.
In everyday speech, lightning is an example of an unusual and unlikely event, as in the saying: “lightning never strikes twice”. This saying is not only false in a literal sense (e.g. it hits the Empire State Building 23 times a year3), but the 3 million daily strikes around the world are common enough to cause thousands of injuries and deaths of people and livestock and cost billions of dollars in damages every year 4. But what are exactly the odds of being struck by lightning? The answer to this question is not as straightforward as it may seem.
There is no database of global lightning deaths, injuries, or damages, and these events have been poorly documented in most countries. Compared to other natural hazards such as hurricanes, tornados, floods, and extreme temperatures, thunderstorms tend to be more localized, last less, and kill fewer people in a single incident, making them less likely to come to the attention of the media or government. Additionally, survivors often do not seek medical care and are not considered in the statistics. It is roughly estimated that 24,000 people are killed by lightning every year. Considering this number and that approximately 90% of the victims survive, the total number of people struck by lightning is estimated to be about 240,000 per year. These figures probably underestimate the real situation because they were calculated by extrapolating incomplete data from almost 20 years ago, and the 90% survival rate is unlikely to apply globally4.
Better estimates can be made at the national level, as there are relatively up-to-date and complete data for some countries such as the US or UK. The odds of being struck by lightning in a given year in the US are approximately 1 in 1,2 million5. Although this is a very unlikely event, the odds of it happening at least once over an 80-year lifetime is much higher: 1 in 15,000. Due to natural and social factors, lightning risk varies widely, depending on the geographic area, period, and other circumstances. For example, in the UK, the risk of being struck by lightning in a year, based on data from 2007 to 2016, is around 1 in 5 to 6 million6, a much lower chance than in the US. In fact, the higher lightning incidence per area in the US makes it six times more likely to be killed by lightning there than in the UK7.
Even in the same locality, the odds also change a lot throughout the year. For example, 87% of lightning deaths in the UK happens in spring and summer, when most of the major thunderstorm occurs6. In general, this kind of seasonal pattern occurs worldwide; while cases are peaking in the Northern Hemisphere summer, they are at their lowest level in the Southern Hemisphere Winter and vice versa4.
Social factors also affect the chance of suffering a lightning accident. People in less developed rural areas are more vulnerable due to the lack of lightning-safe structures, the prevalence of outdoor work (e.g. agriculture) and less education about lightning safety 4. A study8 found that the number of lightning fatalities per million people is four times higher in Brazil than the average of developed countries (0.8 compared to 0.2). This study also showed that 19% of these fatalities happened during rural activities and 15% inside houses. In contrast, lightning has not killed anyone indoors in the 30 years between 1987 to 2016 in the UK6. A sad example of the importance of lightning-safe buildings is the occurrence of lightning accidents with multiple victims in African schools. In a particularly terrible case, a single strike killed 19 people and injured 50 others inside a classroom in Uganda9. In general, lightning accidents have been declining over the last century in the developed world, but not in lesser developed regions 4.
Men tend to be victims of lightning accidents far more often than women. In the US, 80% of people killed by lightning between 2006 and 2019 were men10 (i.e. they were four times more likely to be killed than women). The numbers are very similar in the UK: males accounted for 83% of lightning fatalities from 1987 to 20166. This difference is probably related to men being less careful about lightning and more prone to risky behavior.
At an individual level, different activities and behaviors strongly affect the chance of being hit by lightning. A recent review on lightning safety4 presents the following three principles to evaluate and reduce the risk of an accident.
The first principle is to always assume that a place is unsafe until you know for certain that it is safe. The only reliably safe places are 1) inside large buildings with plumbing, wiring, or metal building components coursing through the walls or 2) a fully enclosed metal-topped vehicle. The energy of a lightning strike moves around this type of place, not affecting the people inside it, although touching wiring or plumbing during a strike can still result in injuries. Being outdoors near a thunderstorm is always dangerous, but some activities are riskier. In the US, more than half of the lightning deaths (62%) occur during outdoor leisure activities, of these, 35% are water-related, and 14% are sports-related. These activities happen in open and unprotected spaces, distant from a safe shelter. Also, lightning tends to strike the tallest object in an area, which in these environments are often people.
The second principle is to know that rain avoidance is not the same as lightning safety. During rain, people often seek shelters that protect them from being wet but do not offer protection against lightning, such as trees, tents, bus stops, or other small and open-sided structures. In fact, seeking shelter under trees is so dangerous that 10% of all lightning casualties in the developed world happen in this situation. Even if trees or similar shelters can offer some protection against a direct strike, most lightning accidents occur through indirect mechanisms (95 – 97% of the fatalities). For example, 40 – 50% of all fatalities happen when lightning strikes a distance away from the victim and then travels through the ground (“ground current”), and 20 – 30% of all fatalities occur when lightning first hits an object and then jumps to a nearby person (“side flash” or “splash”). It is also important to know that sometimes lightning hits the ground miles away from the thunderstorm it came from, striking an area with no overhead clouds, so it is advisable to stop outdoor activities not only during rain but also while a storm is still near4.
The third principle is to know that myths about lightning safety are more often wrong than correct. Some of these popular misconceptions are harmless, such as believing that mirrors should be covered during thunderstorms, but others can provide a dangerous sense of false security, such as believing that only direct strikes cause accidents or that rubber mats or shoes protect from injury or death. It is essential to obtain information from trusted sources, like the National Weather Service in the US or the Royal Society for the Prevention of Accidents (RoSPA) in the UK.
It is very unlikely that you will be struck by lightning in your lifetime, but that is no reason to be careless. In addition to being potentially deadly, lightning strikes often result in severe burns, damage to different organs, longstanding neurological and psychological problems, and disabilities4, and cause intense suffering to several thousand victims and their families every year. Fortunately, lightning accidents do not need to be seen as a dangerous lottery but as a risk that depends on our actions and can be dramatically reduced by avoiding certain situations and behaviors and promoting natural hazards education and lightning-safe infrastructure.
References
1. Jensenius, J. S. Understanding Lightning. https://www.weather.gov/safety/lightning-science-scienceintro
2. The Editors of Encyclopaedia Britannica. Lightning. Encyclopaedia Britannica https://www.britannica.com/science/lightning-meteorology (2022).
3. National Weather Service. Lightning Myths. https://www.weather.gov/safety/lightning-myths.
4. Cooper, M. A. & Holle, R. L. Reducing Lightning Injuries Worldwide. Springer Natural Hazards (Springer International Publishing, 2019). https://doi.org/10.1007/978-3-319-77563-0
5. National Weather Service. How dangerous is lightning? https://www.weather.gov/safety/lightning-odds
6. Elsom, D. M. & Webb, J. Lightning deaths in the UK: a 30-year analysis of the factors contributing to people being struck and killed. Int. J. Meteorol. 42, 8–26 (2017). https://core.ac.uk/download/pdf/220157056.pdf
7. Elsom, D. M., Enno, S., Horseman, A. & Webb, J. D. C. Compiling lightning counts for the UK land area and an assessment of the lightning risk facing UK inhabitants. Weather 73, 171–179 (2018). https://doi.org/10.1002/wea.3077
8. Cardoso, I., Pinto, O., Pinto, I. R. C. A. & Holle, R. Lightning casualty demographics in Brazil and their implications for safety rules. Atmos. Res. 135–136, 374–379 (2014). https://doi.org/10.1016/j.atmosres.2012.12.006
9. Mary, A. K. & Gomes, C. Lightning accidents in Uganda. in 2012 31st International Conference on Lightning Protection, ICLP 2012 (2012). https://doi.org/10.1109/ICLP.2012.6344235
10. Jensenius, J. S. A detailed analysis of lightning deaths in the United States from 2006 to 2019. vol. 21 (2020). https://www.weather.gov/media/safety/Analysis06-19.pdf