The Delhi government plans to try cloud seeding again.
Here, we take you through the aims of the project and why it failed.
What is cloud-seeding, and how is it done?
To create artificial rain, water droplets in clouds are “seeded” with chemicals.
The droplets cluster around those chemical particles and eventually grow heavy enough to fall down as rain.
Cloud-seeding works when there is at least 50% moisture in the cloud, but those targeted in the Delhi experiment only had around 15%, said Manindra Agrawal, director of the Indian Institute of Technology, Kanpur, which partnered with the government for the project.
In a televised interview, Agrawal said his team used a chemical mixture made of common salt, rock salt and silver iodide.
Cloud-seeding technology is not new.
Beijing used the technique to clean the city’s air during the 2008 Olympics.
India has seeded clouds before, in states such as Karnataka, Tamil Nadu and Maharashtra, to manage droughts and address water scarcity.
The Delhi project was the first time India tried to use cloud-seeding to minimise air pollution, Agrawal said in an interview to local media.
What was Delhi’s plan?
Last month, the Delhi government combined efforts with IIT Kanpur to launch the cloud-seeding experiment at an estimated cost of around US$400,000 ($698,700).
The first trial was conducted on October 23 and two more on October 28.
Scientists expected rainfall within four hours of injecting the clouds, but none of the trials produced the expected results.
The chemical mixture was dispersed over six neighbourhoods in Delhi’s outer regions using flares attached to the wings of an aircraft.
Manjinder Singh Sirsa, the Environment Minister for Delhi, said the next trial will be conducted once the moisture level exceeds the current reading.
Had the recent efforts been successful, the government would likely have conducted multiple rounds until February, when the air starts improving, Sirsa said.
There is some debate on whether cloud-seeding can succeed in Delhi.
Last year, the Indian Government’s Environment Ministry said the process would not work in Delhi during cooler months.
“Effective cloud-seeding requires specific cloud conditions, which are generally absent during Delhi’s cold and dry winter months,” it said.
Why is Delhi so polluted at this time of year?
It’s part geography and part human activity.
Delhi sits in a landlocked plain surrounded by mountains and plateaus. Its bowl-like topography traps pollutants, and because its winters are dry and windless, there is very little to disperse toxic particles.
The Delhi metropolitan area is also enormous, with roughly 33 million people.
It is dusty because buildings are constantly being demolished or constructed. Vehicles of every type, from motorcycles to giant trucks, weave through the city.
In the autumn, fireworks are set off during the festival season around Diwali, the Hindu festival of lights that fell on October 21 this year.
And north-westerly winds carry smoke from stubble burning in two heavily agricultural neighbouring states, adding to the city’s concentration of harmful particulate matter.
The air quality index in the past week has hovered at around 350, or the “very poor” category, in many parts of the capital and can cross into the “hazardous” range multiple times in a season.
“This city is unliveable around the year, especially for the poor who don’t have air purifiers and ACs,” said Jasvinder Singh, 57, a cabdriver.
Summers are too hot, but winters are filled with polluted air, he said.
“If it rains, it rains too much,” Singh, a lifelong resident, said. “Now it is not raining, but we want it to rain.”
This article originally appeared in The New York Times.
Written by: Anupreeta Das and Pragati K.B.
Photograph by: Bryan Denton
©2025 THE NEW YORK TIMES
