CHENNAI: Since 14 people have been killed by lightning strikes since the onset of the northeast monsoon, meteorologists have urged the public to remain alert during thunderstorms, particularly in the initial phase of the rainy season, when changing atmospheric conditions can trigger frequent lightning.

Also, State Revenue Minister KA Sengottaiyan said on October 26 that 14 people had died in lightning strikes since monsoon began, even as intensifying rains triggered red alerts and prompted authorities to restrict tourist entry to major hill stations.

Meteorological experts have urged the public to exercise caution during thunderstorms, particularly in the initial phase of the northeast monsoon, when lightning activity can pose a serious threat to people working or travelling outdoors.

According to the National Crime Records Bureau’s (NCRB) 2024 data, 2,825 people died due to lightning strikes across India. Madhya Pradesh recorded the highest number of deaths, at 577, while Tamil Nadu reported 66 fatalities, ranking 13th among states.

Explaining the meteorological factors behind lightning, VR Durai, director, Regional Meteorological Centre, Chennai, told DT Next that cumulonimbus clouds are primarily associated with thunderstorms and lightning. “Cumulonimbus clouds are among the largest and most vertically developed clouds in the atmosphere. They can extend to heights of 6,000 to 16,000 metres or even higher into the upper troposphere. The electrical processes within these storm clouds generate lightning,” he explained. “Lightning activity can be frequent during the initial phase of the monsoon due to prevailing weather conditions. That’s why public awareness is important, particularly when thunderstorms occur alongside heavy rainfall.”

Private weather enthusiast R Hemachandran, popularly known as Delta Weatherman, said that Tamil Nadu generally experiences two periods of increased lightning activity: April and May, during the summer thunderstorm season, and the transition from the Southwest monsoon to the Northeast monsoon, particularly around September and October. “During these periods, changes in wind patterns and atmospheric conditions can favour the development of thunderstorms and lightning. The initial phase of the monsoon can witness frequent lightning. Its frequency may decline after the monsoon becomes established, although lightning can still occur,” he said.

Experts cautioned that rainfall alone should not be considered an indicator of safety, as lightning can strike even when heavy rain is not occurring directly overhead. The India Meteorological Department (IMD), in its thunderstorm and lightning safety guidelines, advises people to move indoors immediately upon hearing thunder. Those outdoors should seek shelter in a substantial building or an enclosed vehicle and avoid taking refuge under trees, near electric poles or beneath metal structures.

People should also move away from water bodies and avoid open fields, elevated locations and exposed hilltops during thunderstorms. The IMD further advises people indoors to stay away from windows, doors and electrical conductors, and to avoid bathing or using running water during a thunderstorm.

People should unplug unnecessary electrical appliances where it is safe to do so, follow official weather warnings and remain indoors for at least 30 minutes after the last thunderclap before resuming outdoor activities.

Despite the recurring threat, a lack of awareness about lightning safety remains a concern. According to NCRB data cited in the report, India recorded over 1.02 lakh deaths due to lightning over the 50 year period from 1975 to 2024.

With lightning posing a recurring risk during Tamil Nadu’s seasonal thunderstorms, experts said greater awareness of weather alerts and adherence to basic safety precautions could help prevent avoidable fatalities