At an airstrip, a modified Cessna 206-H aircraft stands ready. On its wings are small canisters filled with a mix of chemical salt particles. Inside, meteorologists and engineers from Indian Institute of Technology (IIT) Kanpur monitor weather data, watching for the right moment when the humidity and cloud height align perfectly.
When the India Meteorological Department (IMD) gives its signal, the aircraft takes off, climbing to specific heights of several thousand feet. Once positioned under or within clouds, the seeding flares are ignited.
Inside the cloud, invisible water droplets begin to form and grow as they combine with each other; the salt particles encourage the droplets to merge and grow heavier. If all works as expected, within minutes or hours, the droplets begin to fall. First, a drizzle, then in a steady shower. From the ground, it looks like natural rain, but it’s one nudged into existence by science.
In a bid to wash out ambient pollution and smog, this is what the Delhi government hopes to accomplish with its cloud seeding operation, a method that has been around since the 1940s. As the national capital once again struggles under a blanket of post-Diwali smog, the city government is preparing to experiment with artificial rain for the first time. Chief Minister Rekha Gupta announced on October 23 that if weather conditions stay favourable, Delhi could witness its first-ever cloud seeding-induced rainfall on Wednesday.
However, Delhi Environment Minister Manjinder Singh Sirsa confirmed that cloud-seeding would take place on Tuesday (October 28) as the weather conditions are favourable. "The flight will arrive in Delhi once the visibility improves (in Kanpur). The cloud seeding trial will be conducted today," he told PTI.
Delhi’s air quality index (AQI) climbed to an average of 395 on October 21 after Diwali celebrations, placing it in the severe category; PM2.5 levels peaked at 675 µg/m³ on Diwali night. Thirty-six of the city’s 38 monitoring stations reported “red zone” readings, marking one of the worst pollution spikes in recent years. By comparison, post-Diwali AQI levels were 328 in 2024, 218 in 2023, and 312 in 2022.
The Delhi government is working in collaboration with IIT Kanpur’s Department of Aerospace Engineering and the Indian Institute of Tropical Meteorology (IITM), Pune.
2. Glaciogenic seeding: This uses silver iodide or dry ice to promote ice crystal formation in colder clouds, which melt into rain as they descend.The success of the operation depends on the weather and suitable cloud conditions.
Gupta in a post on X earlier in October, said, "This initiative is not only historic from a technical perspective but is also set to establish a scientific method to combat pollution in Delhi. The government's objective is to make the capital's air clean and the environment balanced through this innovation."
On October 23, a test flight to check aircraft readiness and coordination between teams was conducted over the Burari area near northern Delhi. Delhi’s Environment Minister shared videos of the exercise, stating, "This flight was the proving flight for checking the capabilities for cloud seeding, the readiness and endurance of the aircraft, the capability assessment of the cloud seeding fitments and flares, and coordination among all involved agencies."
According to IMD, cloudy conditions are expected between October 28 and 30, offering the first opportunity to attempt full-scale seeding and possibly induce rain.
There are also scientific and environmental uncertainties. It is difficult to isolate the impact of cloud seeding from natural rainfall, and repeated use of compounds like silver iodide could, over time, accumulate in soil and water. The Central Pollution Control Board (CPCB) and the Commission for Air Quality Management (CAQM) have both described cloud seeding as an experimental measure that can be viewed as a supporting effort rather than a core pollution-control strategy.
Cloud seeding, however, isn’t new to India, and has been used for decades in Maharashtra, Karnataka, Andhra Pradesh, Gujarat, and Tamil Nadu, mostly to combat drought. The findings from the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) indicate that rainfall can be enhanced by up to 46 percent under the right conditions, according to a report shared in Parliament earlier this year by the Ministry of Earth Sciences (MoES). The study cited was carried out by IITM between 2018 and 2019 over the rain-shadow region of Solapur in Maharashtra.
The research found that potential applications of cloud seeding include water catchment management, fog and hail suppression, and weather modification during extreme events. However, it cautioned that significant uncertainty remains in predicting the results from such interventions.
IITM, under the MoES’s Mission Mausam, is developing technologies in collaboration with industry and startups to advance weather modification research. These include a 16 metre-tall cloud chamber, cloud seeding drones, and dispenser systems.
Cloud-seeding over Delhi is tentatively scheduled for today. However, this may change, depending on weather conditions. The government plans to assess the trial’s impact before deciding on future applications. If Delhi’s upcoming seeding attempt succeeds, it could open the doors for new ways to combat the city’s air pollution.
(With inputs from PTI)
First Published: Oct 28, 2025, 11:12
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