India, Feb. 4 -- At least 180 flights were delayed on Wednesday as shallow to moderate fog enveloped parts of Delhi, the air quality deteriorated to the "very poor" category, and the minimum temperature dipped 0.2 degrees below the normal to 8.2degC.The visibility dropped to 600m at Palam and 450m at Safdarjung at 9am. Clear skies and sustained surface winds of 10-20 kmph were expected for the rest of the day.

An Air Quality Index (AQI) of 327 (very poor) was recorded at 9am, compared to the 24-hour average of 272 (poor) at 4pm on Tuesday.The Air Quality Early Warning System (AQEWS) for Delhi said the AQI was likely to improve to the "poor" zone later on Wednesday, thanks to surface winds, and the "moderate" category on Thursday and Frid...