Delhi woke to a dense blanket of pollutants and shallow fog on Friday morning as the national capital continued to experience deteriorating air quality and a steady drop in temperatures, signalling an early onset of winter conditions. The minimum temperature was recorded at 12.7°C, which is two degrees below the seasonal normal. Meteorologists attributed the cooling trend to persistent cold northwesterly winds and clear nighttime skies, factors that together set the stage for colder nights over the weekend. According to the India Meteorological Department (IMD), the temperature could dip by another one to two degrees in the coming days, with the minimum expected to fall below 10°C by Monday. Thursday marked the first time this season that Delhi’s mercury dipped below 15°C.

An IMD official explained that the sequence of events leading to this temperature drop is typical for this time of the year. Snowfall in the western Himalayas often triggers strong northwesterly winds that sweep into the plains, carrying colder air masses. These winds, combined with cloudless skies, accelerate nighttime radiative cooling, causing surface temperatures to fall more rapidly than usual. As a result, the capital has begun experiencing distinctly colder mornings and evenings even as the daytime warmth persists.

In addition to the temperature dip, Delhi remained engulfed in a thick haze and shallow fog during the early hours, severely limiting visibility until around 9 a.m. when sunlight gradually dispersed the smog. Weather stations under the IMD network recorded varying temperatures across the city, with Lodhi Road registering the lowest minimum at 11.2°C, followed closely by Ayanagar at 11.4°C. Despite the sunshine later in the day, air quality remained firmly in the “very poor” category.

At 9 a.m., the city’s 24-hour rolling average Air Quality Index (AQI) stood at 309. Of the 39 active monitoring stations in Delhi, 26 recorded AQI levels above 300, while the remaining 13 were in the 201–300 range, indicating “poor” to “very poor” air quality. At 4 p.m. on Thursday, the AQI had already been recorded at 311, continuing a pattern of hazardous air quality readings across the week.

An analysis conducted by Hindustan Times of the air quality data from these 39 monitoring stations on November 5 revealed several issues that could be obscuring the true severity of Delhi’s air pollution. The analysis found missing data from some stations, irregular measurement patterns in others, and algorithmic gaps in how the citywide average AQI is calculated. These discrepancies suggest that the official AQI numbers may be underestimating the actual pollution levels that residents are breathing.

Pollution levels rose sharply on Thursday, with the AQI jumping by more than 100 points in a single day. This surge was driven by a combination of factors: the intrusion of smoke from stubble burning in neighbouring states, firecracker emissions from Gurpurab celebrations, and Delhi’s own traffic and industrial pollution. The city experienced a smoke-laden sky for several hours until the wind speed picked up around mid-morning, helping disperse some of the accumulated pollutants.

Data from the Decision Support System (DSS), which tracks external pollution sources, showed that stubble smoke contributed 9.5 percent to Delhi’s total pollution load on Thursday, the highest contribution of the season so far. The DSS forecast indicated an even more significant spike in the days ahead, with stubble smoke expected to contribute 38 percent on Friday, followed by 25.30 percent on Saturday and 31.76 percent on Sunday. Prior to Thursday, the season’s highest stubble smoke contribution was 5.87 percent, recorded on October 28.

Historical data reinforces the pattern of stubble burning becoming a major pollution factor in early November each year. In 2024, the peak single-day contribution of stubble smoke to Delhi’s AQI was 35.1 percent on November 1. In 2023, the peak was recorded at 35 percent on November 3, identical to the 2022 peak. In 2021, stubble burning accounted for as much as 48 percent of Delhi’s total pollution on November 6. These numbers illustrate the entrenched annual trend in which agricultural fires in Punjab and Haryana fuel severe pollution episodes in the capital.

Despite widespread flooding in Punjab earlier this year, which delayed harvesting and consequently the burning of crop residue, the pattern appears to be intensifying. Satellite images have begun detecting increasingly large clusters of red dots representing fire activity. As the burning season accelerates, its impact on Delhi’s air quality is becoming more pronounced with every passing day.

Environmental experts have warned that conditions in the capital are likely to worsen before they improve. Sunil Dahiya, founder and lead analyst at EnviroCatalysts, said that a combination of local and external emissions contributed to the spike in pollution late Wednesday night. According to him, pollutants from firecrackers, vehicle exhaust, and industrial activity accumulated in the stagnant air, as wind speeds remained low until early Thursday morning. It was only around noon that winds became strong enough to disperse some of the trapped particulates.

Dahiya added that meteorological forecasts indicate westerly and northwesterly winds at the transport level will continue to blow into Delhi over the next few days, carrying stubble smoke from agricultural fields in Punjab and Haryana into the city. This movement of pollutants at higher altitudes, followed by their downward mixing into surface-level air, is expected to make stubble burning a dominant factor in Delhi’s worsening air quality through the weekend.

The converging effects of cold winds, increased moisture, accumulating pollutants and seasonal agricultural fires have once again combined to create a bleak environmental outlook for the capital. The thick morning haze, falling temperatures, high AQI levels, and forecasts of rising stubble smoke contributions underline a period of poor air quality that is likely to persist for several days.

As the national capital enters this challenging phase, health experts continue to advise residents—particularly children, the elderly, and individuals with respiratory or cardiovascular conditions—to limit outdoor exposure, use protective masks when necessary, and consider air purifiers for indoor spaces. The coming week, marked by both deeper winter conditions and intensifying pollution sources, is expected to test the resilience of the city and its residents once again.

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