Cloud seeding’s potential to ease drought is uncertain

Karnataka recorded a 35% rainfall deficit between June 1 and September 30, 2026.
The government launched a 60-day cloud-seeding programme to address the state’s rainfall deficit, despite warnings of unfavourable conditions.
Weather experts have called for caution, noting that there may be too few rain-bearing clouds to seed. They also raise concerns about limited public communication on this effort.

The Karnataka government launched a cloud-seeding programme in September to address rainfall deficits in drought-affected parts of the state. Since the launch of the programme, worth around ₹28 crore (₹285 million), questions have been raised about the viability of cloud-seeding operations this late in the monsoon.

Cloud seeding is a disputed weather modification technique that introduces particles into suitable existing clouds to influence how precipitation forms. It cannot create new clouds, and its effect on rainfall is difficult to measure.

Weather experts, including senior IMD officials, have cautioned that “conditions are not favourable” for cloud seeding in Karnataka.

Highest rainfall deficit on record

“For the people of Karnataka, drought is a very common feature,” says G.S. Srinivasa Reddy, former director of the Karnataka State Natural Disaster Monitoring Centre (KSNDMC), who has 35 years of experience in real-time weather monitoring.

Since the turn of the 21st century, Reddy says, 17 of the 26 years have been drought years in Karnataka. But 2026 has been particularly severe, as the state recorded just 551 millimetres of rainfall between June 1 and September 30, a record 35% rainfall deficit. According to the KSNDMC, 30 districts and 209 taluks in the state recorded rainfall ranging from “deficit” to “large deficit” in the June to September period.

The India Meteorological Department (IMD) forecast notes that 2026 will be an El Niño year, and, according to Reddy, almost 60% of Karnataka’s drought years have coincided with El Niño.

Cloud seeding’s potential to ease drought is uncertain — A bird’s eye view of agricultural fields in Karnataka. Since 2000, 17 of the 26 years have been drought years in the state, according to experts. This year was particularly severe, with the state recording 35% rainfall deficit. Image by Anil Sharma via Pexels.

Limitations in measuring rain from a seeded cloud

Karnataka has previously carried out cloud-seeding programmes in 2003, 2017 and 2019.

This year, the Water Resources Department has undertaken the initiative, called the Karnataka Emergency Cloud Seeding Programme 2026. It is supported by a monitoring committee and a technical advisory and evaluation committee, whose members include officers from the Karnataka State Natural Disaster Monitoring Centre (KSNDMC), Karnataka Neeravari Nigam Limited (KNNL) and the Rural Development and Panchayat Raj (RDPR) Department.

“Cloud seeding can be thought of as a way of disturbing a water-heavy cloud to the point where it produces rainfall,” says S.T. Aruna, chief scientist at the CSIR-National Aerospace Laboratories (NAL), Bengaluru, and the corresponding author of a recent paper on cloud seeding science.

However, the rainfall depends on the cloud properties and atmospheric conditions.

Clouds can be classified into three categories depending on their temperature: warm clouds (above 0°C), mixed-phase clouds (between 0°C and -40°C), and glaciated clouds (below -40°C).

When a cloud is in a mixed phase, it contains both ice and water, “as crystals and supercooled water, respectively”, the paper says. Under the right conditions, they interact to form ice crystals via the Wegener-Bergeron-Findeisen (WBF) process.

Ice crystal formation begins with an ice nucleating particle (or ice nucleus). In cases where the nuclei are insufficient, cloud seeding is done by introducing particles into these clouds that water droplets can cling to and accumulate around, Aruna said. “As these particles move around in a cloud, they accumulate more and more water until they become heavy enough to precipitate.”

There are many ways to introduce nucleating particles into clouds, from ground-based generators that produce aerosol particles to rockets and artillery shells that transport these nuclei to the cloud, says Aruna. But the most common method used in India is to fly an aircraft that releases particles directly at the base of clouds. “A light aircraft, such as a Cessna, is fitted with apparatuses like flare racks that can be made to burn substances at the appropriate altitudes, directly releasing the aerosol into the cloud,” she says.

However, Aruna notes that it’s not easy to calculate cloud-seeding efficiency. “How much extra rain it induces versus how much would’ve rained anyway is under debate,” she says.

Rainfall enhancement by cloud seeding is evaluated by using a network of rain gauges in areas where clouds have been seeded and measuring the rainfall at the surface, says Thara Prabhakaran, Scientist-G at IITM, Pune. But this rests on the assumption that the measured rainfall is specifically from the seeded clouds, she says.

Rain clouds over Bengaluru city. Cloud seeding can be understood as disturbing a water-heavy cloud to the point where it produces rainfall. But it depends on the cloud properties and atmospheric conditions. Representative image by P. Jeganathan via Wikimedia Commons (CC BY-SA 4.0).

Project Varshadhare, a cloud-seeding operation conducted in Karnataka from August 21 to November 7, 2017, reported an estimated “average enhancement of 27.9% above the natural rainfall”, as per a 2019 study by the Indian Institute of Tropical Meteorology (IITM), Pune which looked at station level data within four hours after a cloud seeding experiment.

In a separate study, IITM also examined the feasibility and effectiveness of cloud seeding, as part of the fourth phase of the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX). It found that rainfall could be enhanced by 18% on average over a 100-square-kilometre area in the rain shadow region of Solapur, Maharashtra, though it noted that there are large uncertainties to cloud seeding, depending on the cloud dynamics and background aerosol content.

Compared with the Karnataka study, the Solapur experiment has a larger sample size, so should be more accurate, says Madhavan Nair Rajeevan, a scientist with 38 years of experience in weather and climate research, and a former director of IITM, Pune. However, he questions whether “a surplus of 18% rainfall” would be sufficient for drought management in an area like Solapur, “where serious water stress is experienced”.

Cloud conditions may not be optimal for cloud seeding

Cloud seeding needs specific atmospheric and cloud conditions to work.

While Rajeevan did not comment on Karnataka’s latest programme itself, he stressed that “artificial rain cannot be generated with no clouds or little cloud development.”

With the southwest monsoon, which accounts for nearly 75% of Karnataka’s rainfall, already retreating from India, there may be too few rain-bearing clouds for cloud-seeding operations, adds Reddy. As an El Niño year, cyclone impact will also be limited, he says, indicating that there won’t be much rain for the rest of the year in Karnataka.

Reddy also notes a lack of communication from the state to the public. He says that the KSNDMC used to issue daily reports during earlier cloud-seeding operations. He also stresses the importance of accurate radar data for cloud-seeding operations. For the Varshadhare programme, for example, the monitoring institute had installed three Doppler weather radars in the state to monitor cloud thickness, cloud density and other parameters. But this time, the state is solely dependent on pre-existing radars in Goa, Hyderabad and Chennai.

Monsoon rain clouds over the Cauvery river in Mandya district, Karnataka. Image by Timothy A. Gonsalves via Wikimedia Commons (CC BY-SA 4.0). — Monsoon rain clouds over the Cauvery river in Mandya district, Karnataka. With the southwest monsoon, which accounts for nearly 75% of the state’s rainfall, already retreating, there may be too few rain-bearing clouds for cloud-seeding operations. Image by Timothy A. Gonsalves via Wikimedia Commons (CC BY-SA 4.0).

Prabhakaran, who was involved with the CAIPEEX programme in Solapur, says success is dependent on identifying clouds suitable for seeding. In the Solapur experiment, IITM researchers found that rain enhancement occurred only in clouds seeded early in their development.

She notes that radar-based cloud identification is also not entirely accurate, as assessing cloud development cycles remains challenging.

Mongabay-India contacted the state water resources department and the KSNDMC director who leads the technical advisory and evaluation committee for comment but did not receive a response. A senior government official on the committee who spoke to Mongabay-India said they had attended only one meeting and had no details to share about the programme.

The Water Resources Minister has said that the state is “not worried about the financial burden” of the ₹285 million project. But if the programme fails to mitigate the rainfall deficit, Aruna expects questions to arise about whether the funding should have been used elsewhere.

Aruna says the programme should be viewed with “sceptical optimism”, while acknowledging it may not produce the intended results for reasons “out of the realm of human control.”

Banner image: A light aircraft such as a Cessna, fitted with flare racks that can burn substances at appropriate altitudes, is used to release aerosol particles into clouds for cloud seeding. However, cloud seeding needs specific atmospheric and cloud conditions to work and its effect on rainfall is difficult to measure. Representative image by Christian Jansky via Wikimedia Commons (CC BY-SA 2.5).