A layer of smog engulfed parts of Delhi and NCR on Friday morning. Air quality in the national capital plunged to the far end of the 'poor' category. The city-state's air quality index (AQI) reading at 6 am was 290. As per Safar, Delhi's air quality may improve marginally on Saturday. Safar attributed the dip in air quality to a rise in the contribution of stubble fires. Contribution of stubble-burning to PM 2.5 levels was estimated to be 20% on Thursday. The deterioration is despite the average wind speed being around 10-15 kmph. IMD cited the rise in fire count and a dip in temperature as possible reasons. Delhi had recorded the lowest minimum temperature of the season on Thursday. The minimum temperature was 9.4 degrees Celsius, three notches below normal. IMD said that the minimum temperature may fall further over the weekend. IMD added that the wind speed is, however, likely to remain high until November 21.