For Prelims: Cloud seeding, Air Quality Index, Central Pollution Control Board
For Mains: Environment: Air pollution and air quality; Science and Technology: Weather modification and cloud seeding
Source:
Hindustan
5 facts for one-day exams
SSC, railway, police and teaching exams ask direct questions like these.
- The Indian Institute of Technology Kanpur is assisting Delhi's planned cloud-seeding trial.
- Delhi conducted two cloud-seeding trials on 28 October 2025.
- The earlier trials used silver iodide and sodium chloride particles.
- Delhi's citywide AQI was 350 at 5 p.m. on 12 November 2026.
- Rohini recorded an AQI of 475.
The news
Delhi is preparing for another cloud-seeding trial in the coming days, this time with assistance from the Indian Institute of Technology Kanpur, as the city's air quality index crossed 350 on Thursday evening. Officials said the trial would be conducted only when cloud moisture levels are sufficiently high, and all preparations have been completed. The objective is to explore whether induced rainfall can help control air pollution in the capital.
An official involved in the trial told PTI that the timing depends entirely on weather conditions, particularly the moisture content in clouds. Two previous cloud-seeding trials were conducted on 28 October 2025, using small aircraft to release silver iodide and sodium chloride particles into clouds, but they did not produce rainfall in Delhi and surrounding areas, raising questions about the technique's effectiveness. On Thursday, Delhi recorded its highest AQI since Diwali, with a citywide reading of 350 at 5 p.m., classified as 'very poor' by the Central Pollution Control Board. Ten of the city's 59 monitoring stations recorded AQI above 400, which falls in the 'severe' category, with Rohini at 475 and IIT Delhi at 472.
Why in the news?
Delhi's air quality index reached 350 on 12 November 2026, the highest since Diwali, prompting officials to announce a fresh cloud-seeding trial with IIT Kanpur to explore artificial rain as a pollution-control measure.
How does cloud seeding work?
Cloud seeding is a weather-modification technique in which particles such as silver iodide are introduced into existing clouds. The particles trigger a micro-physical process that encourages the formation of ice crystals or small water droplets, potentially leading to precipitation. The two trials on 28 October 2025 used silver iodide and sodium chloride released from small aircraft but failed to produce rain in Delhi and nearby areas.
What do the AQI readings show?
The Central Pollution Control Board classifies AQI from 301 to 400 as 'very poor' and 401 to 500 as 'severe'. The citywide reading of 350 on Thursday therefore falls in the very poor category, while readings at Rohini (475) and IIT Delhi (472) are in the severe category. The variation between monitoring stations shows that pollution levels are not uniform across the city.
AQI categories
| AQI range | Category |
|---|---|
| 0–50 | Good |
| 51–100 | Satisfactory |
| 101–200 | Moderate |
| 201–300 | Poor |
| 301–400 | Very poor |
| 401–500 | Severe |
Delhi connection
Matters for these Delhi exams:DSSSB
Facts and terms for exams
- Cloud seeding:
- A weather-modification technique that introduces particles into clouds to encourage the formation of ice crystals or water droplets and potentially precipitation.
- Air Quality Index:
- An index that communicates air quality using a numerical value and associated category.
- Central Pollution Control Board:
- India's statutory body concerned with the prevention and control of pollution.
Why it matters for exams
Exams: DSSSB
Syllabus: Environment: Air pollution and air quality; Science and Technology: Weather modification and cloud seeding
Common mistake: Examiners may swap the very poor and severe AQI categories: 350 is very poor, while 475 is severe. A planned cloud-seeding trial is not proof that rainfall occurred.
Mains question
Cloud seeding is being explored as a short-term measure to tackle Delhi's air pollution. Critically evaluate its effectiveness compared to addressing emission sources.
Stuck? Get it in one tap
Cloud seeding means adding particles to existing clouds to encourage rain. Delhi plans to test the technique as a possible way to reduce air pollution, but the trial requires suitable cloud moisture. The earlier trials did not produce rain, so the outcome is not guaranteed.
- The Indian Institute of Technology Kanpur is assisting Delhi's planned cloud-seeding trial.
- Delhi conducted two cloud-seeding trials on 28 October 2025.
- The earlier trials used silver iodide and sodium chloride particles.
- Delhi's citywide AQI was 350 at 5 p.m. on 12 November 2026.
- Rohini recorded an AQI of 475.
- Environment: Air pollution and air quality
- Science and Technology: Weather modification and cloud seeding
Related concepts: Cloud seeding, Air Quality Index, Central Pollution Control Board
Practice questions
Pick an answer, then read the explanation.
- Q1Easy
Which institution is assisting the planned Delhi cloud-seeding trial in November 2026?
Explanation: The Indian Institute of Technology Kanpur is assisting the planned trial. IIT Delhi is a monitoring location, the Central Pollution Control Board provides AQI categories, and monitoring stations record air quality.
- Q2Hard
Consider the following statements about Delhi's cloud-seeding trials:
- 1.The planned trial depends on favourable weather and sufficient cloud moisture.
- 2.The trials on 28 October 2025 produced rainfall in Delhi and nearby areas.
- 3.Silver iodide and sodium chloride particles were used in the 2025 trials.
Which of the statements given above are correct?
Explanation: Statements 1 and 3 are correct: the proposed trial needs suitable conditions, and the earlier trials used both named substances. Statement 2 is incorrect because the 2025 trials did not produce rain in Delhi and nearby areas.
- Q3Medium
What was Delhi's citywide AQI at 5 p.m. on 12 November 2026?
Explanation: Delhi's citywide AQI was 350, which falls in the very poor category. The reading of 475 was recorded at Rohini; 300 and 400 are category boundary values.
- Q4Medium
What is the principal objective of Delhi's planned cloud-seeding trial in November 2026?
Explanation: The trial aims to explore the potential of rainfall for pollution control. It does not replace monitoring, guarantee rain or change AQI categories; its timing depends on favourable weather.
Frequently asked questions
1. Why is Delhi planning another cloud-seeding trial?
The trial aims to explore whether induced rainfall can help control air pollution.
2. Which institution is assisting Delhi's planned cloud-seeding trial?
The Indian Institute of Technology Kanpur is assisting the planned trial.
3. Did Delhi's cloud-seeding trials in October 2025 produce rain?
No. The two trials on 28 October 2025 did not produce rainfall in Delhi and nearby areas.
4. Which AQI category includes a reading of 350?
A reading of 350 falls in the very poor category, covering AQI values from 301 to 400.
All sources
- Original12 November 2026 · Read story
