India, Sept. 30 -- Since September 12, Delhi has seen its longest run of September days where the air quality index (AQI) has stayed above 100 in nearly a decade -- a streak unmatched since 2016, when the city logged 29 such days.

Data from the Central Pollution Control Board (CPCB) shows the contrast clearly. Delhi recorded just five consecutive days above 100 in 2024, 10 each in 2023 and 2022, two in 2021, and 14 in 2020.

For Delhi, where winter pollution often pushes AQI levels beyond 400, an index above 100 may not appear alarming. Yet for September, usually cleaner due to monsoon rains, it signals an unusually polluted month.

Experts said conditions shifted after early September showers gave way to drier northwesterly winds. Rain ...