Delhi AQI rises to 323, IIT-Delhi records severe pollution as calm winds trap pollutants

Delhi's air quality worsened on Thursday, with the national capital recording an Air Quality Index (AQI) of 323 in the morning and remaining in the 'very poor' category. Calm winds and unfavourable weather conditions prevented pollutants from dispersing overnight, leaving them trapped close to the ground.

The Central Pollution Control Board's (CPCB) hourly data showed that Delhi's AQI stood at 321 at 7am before rising to 323 an hour later. The reading was eight points higher than Wednesday's official daily average of 313, indicating a further deterioration in air quality.

The worsening pollution comes as the Commission for Air Quality Management's (CAQM) Stage III measures under the Graded Response Action Plan (GRAP) remain in force across Delhi-NCR. The restrictions, which came into effect on November 6, include curbs on dust-generating construction and demolition activities and measures to limit vehicular and other emissions.

IIT-Delhi records severe air quality

Of the 57 air quality monitoring stations reporting data in Delhi, IIT-Delhi recorded the highest pollution level, with an AQI of 414, placing it in the 'severe' category.

The Cantonment station was the only one to record 'moderate' air quality, with an AQI of 128. The remaining stations reported readings in the 'very poor' category in the station-wise assessment.

Fine particulate matter, or PM2.5, continued to be the principal pollutant, emerging as the leading contributor at 48 of the 57 monitoring stations. High concentrations of these fine particles pose a particular concern because they can penetrate deep into the respiratory system.

Under the CPCB's classification, an AQI between 0 and 50 is considered 'good', 51-100 'satisfactory', 101-200 'moderate', 201-300 'poor', 301-400 'very poor' and 401-500 'severe'.

Warmer nights and stagnant air worsen conditions

Weather conditions have played a significant role in the build-up of pollution. Calm winds during the night restricted the movement of pollutants, while a layer of warmer air above the surface acted as a lid, limiting vertical mixing and keeping emissions concentrated closer to the ground.

Minimum temperatures rose across all five of Delhi's weather stations on Thursday, with readings ranging between 16°C and 17°C, significantly above the seasonal average, according to India Meteorological Department (IMD) data.

Palam recorded the lowest minimum temperature at 16°C, which was 1.8°C above normal. At Safdarjung, the city's base weather station, the minimum settled at 16.5°C, 3°C above normal. Lodhi Road recorded 16.6°C, marking the highest departure from normal among the five stations at 4.6°C.

The Ridge recorded a minimum temperature of 17°C, 1.6°C above normal, while Ayanagar registered 16.6°C, 2.1°C above the seasonal average.

Temperatures also increased at every station compared with Wednesday. Safdarjung and Lodhi Road recorded the sharpest rise, at 1.7°C each. The minimum temperature increased by 1.4°C at the Ridge, 0.8°C at Palam and 0.5°C at Ayanagar.

Shallow fog also affected visibility at Safdarjung and Palam during the morning. At Safdarjung, visibility fell to 800 metres between 6.30am and 8am before improving to 900 metres by 8.30am. At Palam, it remained at 800 metres between 7.30am and 8am and improved to 1,000 metres at 8.30am. No rainfall was recorded at any of the five weather stations.

GRAP Stage III restrictions remain in force

With pollution levels continuing to remain high, Stage III of GRAP is active across the national capital region. The measures include restrictions on non-essential dust-generating construction and demolition work, stone crushers and mining activities, along with steps to intensify dust suppression on roads and other surfaces.

The CAQM has also advised people to use public transport or electric vehicles, avoid open burning of biomass and municipal solid waste, and wear masks when stepping outdoors. Its advisories include hybrid classes for students up to Class V and work-from-home arrangements for offices, as directed by the authorities. Restrictions also apply to certain older vehicles, including BS-III petrol and BS-IV diesel light motor vehicles.

Farm fires remain a seasonal source of pollution

Stubble burning in neighbouring states continues to add to the pollution burden in Delhi-NCR, although the extent to which smoke from farm fires affects the capital varies according to wind direction, wind speed and prevailing atmospheric conditions.

Punjab recorded 2,347 farm-fire incidents up to November 4, compared with 2,839 during the corresponding period last year, a decline of 17.3%, according to a Hindustan Times report published on November 5. However, 11 of the state's 23 districts reported an increase in incidents.

The annual figures also need to be considered in the context of a shift in the timing of stubble burning. In 2025, 98% of the fire heat detected by Meteosat was recorded after 3pm, compared with 94% in 2024. This difference in timing can affect the number of incidents captured by satellite observations.

Both annual counts are believed to be underestimates, as a substantial proportion of the burning now takes place after the satellite passes over the region at around 1.30pm.

More recent satellite observations also point to continuing farm-fire activity in Punjab and Haryana. Data displayed on the Hindustan Times' pollution dashboard showed 226 fires detected on November 5, 147 on November 6, 244 on November 7, 385 on November 8, 324 on November 9, 306 on November 10 and 128 on November 11. These figures cover the two states and are also considered an undercount.

Farm fires are not the only source of pollution affecting the capital. Vehicular emissions and other local sources continue to contribute to the city's poor air quality. When these emissions combine with weak winds and unfavourable atmospheric conditions, pollutants accumulate rather than disperse, making the winter pollution crisis particularly difficult to contain.