Delhi chokes as air quality hits season’s worst, smog to set in before Diwali

Delhi-NCR’s air quality deteriorated to its poorest level of the season on Thursday. The 24-hour average Air Quality Index (AQI) climbed to 245, up from 233 the previous day — marking the third consecutive “poor” air day this week.

Meteorologists warn that pollution levels could worsen over the weekend, coinciding with Diwali celebrations and the rising influence of stubble-burning emissions.

The Air Quality Early Warning System for Delhi has forecast that the city’s air will remain in the ‘poor’ category until Sunday and may slide into the ‘very poor’ zone by October 20. The India Meteorological Department (IMD) has also predicted the onset of smog conditions from Sunday.

Calm winds, falling temperatures

Experts attribute the worsening air to a mix of meteorological and anthropogenic factors.

“Winds are becoming calm at night, and with temperatures dipping, pollutants are getting trapped close to the surface,” Mahesh Palawat, vice-president of Skymet Weather told TOI. “Road traffic is also at a seasonal peak, and calm wind conditions expected on Diwali night could cause firecracker emissions to accumulate.”

On Thursday, Delhi’s minimum temperature dropped to 18.1°C, its lowest this season and the first major dip below 20°C in the 2025–26 winter cycle. The IMD expects the mercury to touch 17°C on Friday, with a maximum temperature near 31°C under clear skies.

Comparatively, the city’s first sub-20°C reading arrived later than in recent years — October 12 in 2024 and October 3 in 2023 — signalling a slightly delayed winter onset this year.

Stubble burning & transport

According to the Decision Support System (DSS) accessed by TOI, transport emissions were the leading contributor to Delhi’s PM2.5 levels on Thursday, accounting for 18.7% of total pollutants.

This was followed by cross-border sources — Sonipat (6.5%) and Gurgaon (4.6%).

The DSS also noted a rising share of stubble burning in Delhi’s pollution mix, increasing from 0.2% on Wednesday to 0.76% on Thursday. The contribution is expected to rise to 3.9% on Friday and 6.4% on Saturday as northwesterly winds bring smoke from Punjab and Haryana into the capital.

Satellite data recorded 132 fire incidents in Uttar Pradesh, 12 in Punjab, and 3 in Haryana on Thursday, suggesting an early uptick in crop-residue burning across the northern plains.

‘Very poor’ air

Data from the Central Pollution Control Board (CPCB) showed that out of 38 monitoring stations in the capital, five recorded “very poor” air quality.

Anand Vihar topped the list with an AQI of 359, followed by Wazirpur (350), Dwarka Sector 8 (313), Delhi University North Campus (307), and CRRI Mathura Road (307).

For context, the CPCB classifies AQI between 201–300 as ‘poor’, 301–400 as ‘very poor’, and above 400 as ‘severe’.

With calm winds, festive emissions, and stubble smoke set to converge in the coming days, Delhi’s air quality is poised to worsen — a familiar prelude to the capital’s annual winter pollution cycle.