Delhi AQI averaged 166 in October 2026, the lowest October reading in eight years, the Union Environment Ministry said on October 31. The figure put the month in the moderate band, compared with poor air in October 2025, when the average stood at 223. Delhi AQI also improved across the first ten months of the year, averaging 167 between January and October, against 170 in the same period of 2025.
Delhi AQI in October compared with past years
The ministry gave the full October series to show how far the reading had fallen. Delhi AQI stood at 223 in October 2025, 234 in 2024, 219 in 2023, 210 in 2022, 173 in 2021, 265 in 2020, 234 in 2019 and 269 in 2018. The 2026 average of 166 was therefore lower than every October since 2018, and the only other October since 2018 to average below 200 was 2021, at 173. The Times of India, using Central Pollution Control Board figures going back to 2015, described it as the lowest October on record.
Between January and October 2026, Delhi recorded 220 days in the good to moderate band, with a daily average below 200. That was more than the 200 such days in the same period of 2025, and the highest number since 2018 apart from 2020, when 224 such days were recorded. Days in the poor to severe-plus band fell to 84 in the first ten months of 2026, down from 104 in 2025.
Why Delhi AQI fell in October
Weather did much of the work, according to researchers quoted by The Times of India. Safdarjung, Delhi’s main weather station, recorded 127.5 mm of rain in October against a normal of 15.1 mm. Anumita Roychowdhury of the Centre for Science and Environment, a Delhi research group, told the paper that the rain washed dust and smoke out of the air, helped pollutants disperse and cut the smoke drifting in from farm fires in neighbouring states. Delhi also had its wettest October day in four years, with 61.4 mm of rain in the 24 hours ending at 8:30 am on October 30, and the daily reading fell to 60 that day.
The comparison also needs care, because Diwali fell in different months in the two years. The festival fell on October 20 in 2025 but falls on November 8 in 2026, so festival-related pollution landed in different months. One analysis cited by The Infra Post found that October 2026 still recorded the lowest average after excluding Diwali and the three following days from the comparison, though the improvement over 2025 was smaller on that basis.
Delhi AQI particles and what winter may bring
The ministry’s figures showed the average PM2.5 concentration between January 1 and October 29 at 69 micrograms per cubic metre, down from 72 in the same period of 2025. PM10 averaged 171 micrograms per cubic metre over the same period, up from 166 a year earlier. The national annual PM2.5 limit stands at 40 micrograms per cubic metre, so the capital’s particle levels remained well above that line even in a better month.
On the 0 to 500 scale used for Delhi AQI, a reading of 166 sits in the moderate band, which means air quality is acceptable but carries some risk for people who are unusually sensitive to pollution. The ministry’s release did not claim the improvement would hold through November and December, when winter conditions usually trap pollutants closer to the ground. Stage I curbs under the Graded Response Action Plan were already in place in the capital, according to a summary of the ministry’s release, and Delhi AQI figures in the coming weeks will show whether the October improvement was mostly weather. The Commission for Air Quality Management said it would intensify its efforts in the coming days.
The Commission for Air Quality Management said it was continuing to work with the relevant authorities to prevent and control pollution across Delhi-NCR and would intensify its efforts in the coming days. Delhi AQI at 166 is still classed as moderate, not clean, and the months ahead will test whether the October improvement was mostly weather or the start of a longer trend. The next monthly release will show whether the capital holds its gains once Diwali pollution and winter smog enter the figures.