NEW DELHI: Delhi's air quality stayed in the 'very poor' category for a fourth straight day on Thursday, with the 24-hour average Air Quality Index at 369 at 4 pm, and forecasts pointing to 'severe' air from Friday through the Diwali weekend.
Wednesday's reading at the same hour was 377; the city averaged 350 on Tuesday and 324 on Monday, according to Central Pollution Control Board data.
Eighteen of the capital's 59 active monitoring stations recorded 'severe' air, with Jahangirpuri the worst at 454. Under CPCB's scale, 301-400 is 'very poor' and above 400 'severe'.
The Air Quality Early Warning System expects Delhi to stay 'very poor' through Thursday and slip to 'severe' from Friday to Sunday, with the six-day outlook at 'severe to very poor'.
The forecast mix is shifting in a way that will not necessarily help. The Decision Support System under the Ministry of Earth Sciences puts stubble burning's contribution at 15.601 per cent on Thursday, rising to 19.201 per cent on Friday and then collapsing to 1.575 per cent on Saturday, while transport's share climbs from 17.913 per cent to 18.291 per cent and 21.108 per cent over the same three days.
Sunil Dahiya of EnviroCatalysts said the fall in the farm-fire share is a weather effect, not a drop in burning. "As a western disturbance moves in, the north-westerly winds that carry smoke from Punjab and Haryana into Delhi are forecast to weaken and turn easterly around Diwali," he said. Punjab has recorded 2,347 farm fires this season, more than 700 of them on November 3 and 4 alone.
Slower winds and morning mist can then trap local emissions from vehicles, industry, waste burning and firecrackers, he said, warning that the smoke can return once the north-westerly winds resume.
With Diwali this weekend, the next three days are the test: the early warning system has already flagged 'severe' air for November 6 and 7.
(With inputs from PTI and media reports)