Delhi's air quality turns 'very poor' for first time this season, AQI crosses 300

Delhi's air quality deteriorated to the 'very poor' category for the first time this season on Monday, with the Air Quality Index (AQI) crossing 300 as a thick layer of haze enveloped the national capital. The deterioration followed a brief improvement last week, when heavy rainfall and strong winds helped clear pollutants from the air.

The city's AQI stood at 307 at 7.05 am on Monday, according to the Central Pollution Control Board (CPCB). This marked a significant deterioration from Sunday's 24-hour average of 261, categorised as 'poor', against 117 in the 'moderate' category a day earlier.

Delhi had recorded an AQI of 60 on Friday, following heavy rainfall that washed away pollutants and resulted in the cleanest October air quality reading in four years.

The deterioration comes even as additional pollution-control measures under the Delhi government's Winter Action Plan came into effect on November 1. With Diwali approaching next week, authorities are concerned that firecracker emissions could further increase the pollution burden.

Jahangirpuri records severe air quality

Of Delhi's 59 air quality monitoring stations, data was available for 58 on Monday. As many as 36 stations recorded 'very poor' air quality, while Jahangirpuri was the only location in the 'severe' category, registering an AQI of 417.

Five monitoring stations reported 'moderate' air quality, while the remaining stations were in the 'poor' category.

The CPCB classifies an AQI between 0 and 50 as 'good', 51 and 100 as 'satisfactory', 101 and 200 as 'moderate', 201 and 300 as 'poor', 301 and 400 as 'very poor', and 401 and 500 as 'severe'.

Delhi last recorded 'very poor' air quality on February 11, when the 24-hour average AQI stood at 305. Before that, the index had touched 339 on February 4.

PM2.5 emerges as dominant pollutant

Fine particulate matter PM2.5 was the primary pollutant at most of Delhi's monitoring stations, according to CPCB data.

At 6 am on Monday, PM2.5 was the dominant pollutant at 51 of the 58 stations reporting data, while PM10 was the primary pollutant at the remaining seven.

A day earlier, PM2.5 was the main pollutant at 46 of the 57 reporting stations, with PM10 dominating at the remaining 11.

The Decision Support System (DSS) for air quality management estimated that stubble burning contributed 18.57% to Delhi's pollution on Sunday, a sharp increase from 5.33% on Saturday. Transport emissions accounted for another 16.4%, while industries contributed around 3%.

NASA detects over 1,300 farm fires in Punjab, Haryana

Satellite data from NASA detected 1,394 farm fires across Punjab and Haryana between October 1 and November 1. Punjab accounted for 1,249 fires, while 145 were recorded in Haryana. As many as 171 farm fires were detected on November 1 alone.

The corresponding figure for the same period last year was 1,861, indicating a decline in the number of detected fires.

However, the figures may not provide a complete picture of stubble burning, as the practice has increasingly shifted to later hours of the day.

Data from Meteosat showed that approximately 98% of the fire heat detected in 2025 occurred after 3 pm, compared with 94% in 2024. Both years' figures are likely to be underestimates because much of the stubble burning now takes place after the satellite passes over the region at around 1.30 pm.

Unfavourable weather likely to worsen pollution

Meteorologist Navdeep Dahiya has warned that the smog season has begun and that unfavourable weather conditions could cause pollution levels to rise further across Delhi-NCR and the northern plains.

In a post on X, Dahiya said most AQI monitoring sensors across Delhi-NCR were reporting readings above 300, with several locations approaching the 400-500 range.

He attributed the worsening conditions to north-westerly winds and calm atmospheric conditions, which allow pollutants to remain suspended in the air for longer periods.

Dahiya also warned that no favourable meteorological conditions were expected over the next seven to 10 days, raising the likelihood of worsening smog across the region.

The Centre's Air Quality Early Warning System has forecast that Delhi's air quality is likely to remain in the 'poor' category on November 2 and 3 before deteriorating to 'very poor' on November 4. The outlook for the following six days also indicates that pollution levels could fluctuate between the 'poor' and 'very poor' categories.

The India Meteorological Department's weather observations showed that Delhi's minimum temperature settled at 18 degrees Celsius on November 1, around 1.9 degrees below the seasonal average. Low temperatures, calm winds and foggy conditions can restrict the dispersion of pollutants, allowing them to accumulate closer to the ground.

With Diwali approaching and farm fires typically increasing during the first week of November, the coming days are expected to remain challenging for the capital's air quality.