Delhi air pollution: Govt conducts two-cloud seeding trials — what happened to experiments worth over ₹1 cr in 2025?

Delhi has carried out two recent cloud-seeding trials near Indira Gandhi International Airport. The exercises were intended to assess whether artificial rainfall could help reduce pollution. Their results have not been officially announced. The government is also unlikely to confirm the proposed operations before Diwali.

The main reported difference was altitude. The latest trials took place at approximately 30,000 metres. The Delhi trials conducted in 2025 operated at nearly 10,000 metres. Cloud seeding still depends on suitable clouds and atmospheric moisture, regardless of flight altitude.

The operations occurred within a 15-day period. Government sources said further attempts are likely after Diwali and Chhath. This suggests Delhi is continuing to test the idea, even though the earlier project with IIT Kanpur failed to produce rainfall and cost more than ₹1 crore.

Delhi’s 2025 cloud-seeding project cost more than ₹1 crore across two sorties. The spending covered the operations conducted with IIT Kanpur to explore artificial rainfall as a possible pollution-control measure. Despite the cost, neither operation achieved its main goal: producing rain.

Each operation released eight chemical flares. The flares contained silver iodide and sodium chloride. These substances were intended to enter suitable clouds and encourage water droplets or ice crystals to form and grow. The chemicals therefore supported a weather process rather than creating rain independently.

The outcome showed the scale of the challenge. The government’s later report linked the failure partly to very low atmospheric moisture, estimated at only 10–15%. The project information also recorded that the government later claimed particulate matter levels had declined in some targeted areas, but rainfall was not generated.

Cloud seeding is a weather-modification technique designed to increase the chances of rainfall or snowfall. It works only by influencing clouds that already exist. This matters because the method is sometimes described as artificial rain, but it does not manufacture clouds or atmospheric moisture from scratch.

Substances such as silver iodide and sodium chloride are dispersed into suitable clouds. Their particles provide surfaces where moisture can gather or freeze. Water droplets or ice crystals then grow. If they become heavy enough, they may fall as rain or other precipitation under favourable conditions.

The technique is therefore conditional, not guaranteed. Its effectiveness depends on cloud composition, moisture content, temperature and prevailing weather. Delhi’s 2025 trials illustrate this limitation: eight flares were used during each operation, but neither exercise produced rainfall because the atmosphere reportedly lacked adequate moisture.

The 2025 trials failed to produce rainfall mainly because the atmosphere did not contain enough moisture. A subsequent government report attributed the result partly to moisture levels of only 10–15%. Such low moisture was not considered favourable for cloud seeding.

The released chemicals needed suitable clouds and moisture to work. Silver iodide and sodium chloride can provide surfaces where water gathers or freezes, forming droplets or ice crystals. Those particles must then grow large enough to fall as precipitation. Without adequate moisture, that chain cannot develop effectively.

The failure does not mean the chemicals were irrelevant. It shows that cloud seeding cannot create rain independently of weather conditions. The government later claimed particulate matter levels declined in some targeted areas, but the primary objective remained unmet. The two sorties cost more than ₹1 crore, and no rainfall was generated.

The Delhi government initiated the artificial-rain project as a possible measure against air pollution. Its Environment Department signed a Memorandum of Understanding with IIT Kanpur on September 25 of the previous year. The agreement focused on exploring whether cloud seeding could induce rainfall in Delhi.

IIT Kanpur was the government’s project partner. The work included two rounds of trials in October. During each operation, eight flares containing silver iodide and sodium chloride were released to encourage precipitation. The government later used project-related information to assess the operations and their cost.

The partnership did not achieve the central aim in 2025. Neither exercise produced rainfall, partly because atmospheric moisture was only 10–15%. The two sorties cost more than ₹1 crore. Delhi has since conducted two more trials near IGI Airport, with further attempts reportedly likely after Diwali and Chhath.

Delhi’s pollution was already serious during the period covered. The capital’s average AQI stood at 369 at 4 pm on Thursday, keeping air quality in the ‘very poor’ category for a fourth straight day. Forecasts warned that pollution could worsen into the ‘severe’ zone from Friday.

Under the CPCB scale, AQI from 301 to 400 is ‘very poor’. A reading from 401 to 500 is ‘severe’. The difference was visible across monitoring locations. Eighteen of Delhi’s 59 operational stations reported severe air quality, while Jahangirpuri recorded the highest reading at 454.

The AQEWS expected very poor air on Thursday and severe conditions from Friday to Sunday. The average AQI had been 377 on Wednesday, 350 on Tuesday and 324 on Monday. These figures show why authorities were examining cloud seeding, although the method’s pollution benefits remained unproven.

Cloud seeding encourages precipitation by working with atmospheric processes that are already present. A cloud must contain suitable conditions for water droplets or ice crystals to form. This matters because seeding is not a way to create a rain system from an otherwise dry atmosphere.

Silver iodide and sodium chloride particles provide surfaces where moisture can gather or freeze. As droplets or ice crystals grow, they may become heavy enough to fall. But that growth requires sufficient moisture, suitable temperatures and an appropriate cloud composition. Prevailing weather also affects whether precipitation can develop.

Delhi’s 2025 experience demonstrates the limitation. Eight flares were released during each operation, but neither produced rainfall. A government report linked the result partly to atmospheric moisture of only 10–15%. The chemicals were present, but the surrounding conditions were not favourable enough to complete the process.