Lightning has killed at least 38 people in India over the past weekend, the Associated Press reports. While the Indian summer has never been a stranger to lightning strikes, these kinds of devastating lightning events have become increasingly more common over the past few decades thanks to climate change.

A senior police officer said 11 of those killed were people "taking selfies" during the thunderstorm near a watchtower at Amber Fort, a famous historical fort in the western state of Rajasthan. At least nine more people were killed and nearly 20 others were injured in separate lightning strikes across the state of Rajasthan. A further 18 people were killed by lightning on Sunday in the northern state of Uttar Pradesh, most of whom are reported to have been working on a farm at the time. 

The summer monsoon season in India runs from June to September each year, characterized by heavy rainfall and humidity. When humidity levels increase and the ground surface temperature is high it creates the ideal conditions for thunder clouds, such as Cumulonimbus clouds.

When Earth’s surface is hot, it heats the air and creates an updraft of warm air to rise. As the air rises through the atmosphere, it cools and forms a cloud. Eventually, it can form an ice-cold cloud, where temperatures are below freezing and the water vapor turns into ice. With warm air continuing to push up from below, this causes tiny ice crystals to rub against each other, building up an electrical charge across the cloud: a negative charge forms at the bottom of the cloud and a positive charge near the top. When the positive and negative charges grow large enough, a rapid discharge of electricity will be released and attracted towards the Earth or other clouds. 

Lightning has always been a feature of the monsoon season, but it appears this phenomenon has recently become more frequent, more intense, and more deadly. According to statistics from India’s National Disaster Management Authority, cited by the Hindustan Times, lightning strikes have killed nearly 2,000 people every year in India since 2004. That figure is almost double the number of annual deaths recorded in the late 1960s.

It’s become increasingly apparent that this uptick in lightning activity is tightly linked to the world’s climate crisis. Not only does climate change result in higher temperatures, but the heat also helps more water evaporate from oceans and lakes, ending up in Earth's atmosphere. A warmer atmosphere can also hold more moisture, further leading to more humidity. Altogether, this is the ideal recipe for more lightning and thunderstorms.  

“Both surface temperature and moisture levels have increased significantly in recent years. Urbanization leading to loss of tree cover also contributes to rise in surface temperature. We think the two have mainly contributed to rise in incidence of lightning. The rise in deaths due to lightning can be because more people are outdoors and possibly exposed to lightning in recent years,” SD Pawar, project director at Thunderstorm Dynamics, the Indian Institute of Tropical Meteorology, told the Hindustan Times.