Delhi’s air quality deteriorated for the fifth consecutive day on Sunday, with the capital recording an average AQI of 187, its worst reading in 82 days and the most polluted start to October in six years. The deterioration comes as the city enters the period when winter pollution typically intensifies.
The Central Pollution Control Board’s 4pm bulletin placed Delhi’s air quality in the upper end of the “moderate” category. The AQI had stood at 171 on Saturday, 174 on Friday and 166 on Thursday. At 9am on Sunday, it was 197 before falling slightly as wind speeds increased.
Dust takes centre stage as winds weaken
PM10 emerged as the dominant pollutant, with coarse inhalable particles linked to road dust, construction activity and farm fires contributing to the deterioration.
The rise followed five consecutive days of “satisfactory” air quality, when rainfall and stronger winds helped disperse pollutants. With the rains receding and local emissions continuing, pollution levels began climbing again.
Jinitha Varghese, programme manager at EnviroCatalysts, said late-September rainfall had temporarily washed particulate pollution from the atmosphere. After the monsoon withdrawal, however, higher daytime temperatures and weaker surface winds caused the wind pattern to shift from moist easterlies to stagnant north-westerlies, trapping local urban dust and regional pollutants close to the ground.
Varghese said year-round reductions in the overall emission load were needed across the air shed. While stubble burning and local dust can trigger seasonal spikes, she said longer-term improvement would require action on emissions from power plants, industrial units, waste management and heavy transport, alongside emergency measures targeting dust and agricultural burning.
Mundka worst hit among monitoring stations
Fourteen of Delhi’s 43 active monitoring stations recorded “poor” air quality in the 4pm bulletin.
Mundka reported the highest AQI at 273, followed by Mathura Road CRRI and Narela, both at 257. Jahangirpuri recorded an AQI of 237.
Delhi Cantonment recorded the cleanest air among the monitoring stations, with an AQI of 97, placing it in the “satisfactory” category.
Under CPCB’s classification, an AQI of 0-50 is “good”, 51-100 “satisfactory”, 101-200 “moderate”, 201-300 “poor”, 301-400 “very poor” and 401-500 “severe”.
2026 records highest early-October average in years
CPCB data shows that Delhi’s average AQI for the first four days of October in 2026 was 174.5, higher than the corresponding averages recorded in recent years.
The figure was 119.75 in 2025, 167.25 in 2024, 155 in 2023, 161.25 in 2022, 107.25 in 2021 and 176.25 in 2020.
Delhi had already begun October on a relatively polluted note, with the October 1 AQI reaching 166. The reading was the highest for the first day of October in four years, according to an analysis by the Centre for Research on Energy and Clean Air.
The capital’s September air quality had, in contrast, been its best average AQI for the month in five years, although PM2.5 and PM10 concentrations had risen. The difference reflected the way the composite AQI is calculated, with the index reflecting the most dominant pollutant rather than the average concentration of all pollutants.
Winter pollution season draws closer
Air quality in Delhi-NCR generally begins deteriorating from around mid-September. Stubble burning is a major seasonal precursor to the winter pollution episode, while fireworks around Diwali can add to pollution despite restrictions that are frequently violated.
The Commission for Air Quality Management has identified PM2.5 as the dominant pollutant affecting Delhi’s air during winter. Secondary particulate matter formed from emissions from vehicles, industries, power plants and biomass burning is also among the major contributors.
Experts have warned that weaker winds as winter approaches could result in more frequent polluted days.
Rain could offer temporary relief
Delhi recorded a minimum temperature of 24.1°C on Sunday, while the maximum temperature reached 36.4°C.
The India Meteorological Department has forecast a gradual fall in the minimum temperature to around 21-23°C during the week. Clear skies are expected on Monday, followed by partly cloudy conditions from Tuesday, with a possibility of very light rain associated with a western disturbance.
Amateur meteorologist Navdeep Dahiya said a series of mild western disturbances could begin affecting the region from October 7. He forecast the possibility of a moderate western disturbance after October 20, which could bring precipitation to the plains of north India and early snowfall in the western Himalayas.
Dahiya said the next significant fall in temperatures was expected after October 10, with isolated rain on October 7-8 potentially causing a minor dip earlier.
Any rainfall could temporarily improve Delhi’s AQI by helping remove particulate matter from the atmosphere.
CAQM finds 17 dust, C&D waste violations
As pollution levels rise, the Commission for Air Quality Management has also intensified inspections of dust sources.
Four CAQM flying squads inspected 25 stretches covering about 35km of Delhi’s Inner and Outer Ring Road on Saturday under its “Operation Clean Air” initiative. They identified 17 violations involving visible road dust and the accumulation of construction and demolition waste.
The commission said the findings showed the need for stricter implementation of prescribed road-cleaning, sweeping and dust-control measures. Accumulated dust and C&D waste on roadsides and carriageways can be resuspended by moving vehicles and contribute to ambient pollution.
The Public Works Department and other agencies responsible for the roads have been directed to take corrective measures on a priority basis. They have also been told to ensure regular sweeping, remove accumulated dust and C&D waste, and maintain road stretches in a clean and dust-free condition.
CAQM said such inspection drives under Operation Clean Air would continue across Delhi-NCR to identify gaps in implementation and facilitate corrective action.
The Delhi government has separately launched an Integrated Command and Control Centre to monitor pollution sources in real time using AI-based analysis. The system will track air quality data, road sweeping and pollution sources, while field teams will monitor construction sites and act against violations including road dust, open burning and construction-related pollution.
With temperatures expected to fall and wind speeds likely to weaken as winter approaches, experts say the coming weeks will be crucial in determining whether the current deterioration remains temporary or develops into Delhi’s familiar winter pollution build-up.