New Delhi, Nov 24 : Delhi-NCR's Air Quality Index (AQI), which registered a slight improvement by falling under the 'poor' category, is likely to return to the 'very poor' category due to a change in the wind direction from Wednesday onwards In its latest bulletin, the Air Quality Early Warning System for Delhi (Ministry of Earth Sciences) said: "The predominant surface wind is likely to be coming from Northwest direction during daytime and from Northeast direction during evening/night with wind speed 05-10 kmph and mainly clear sky on November 23. "The predominant surface wind is likely to be coming from the Southeast direction of Delhi with wind speed 05-10 kmph, mainly clear sky and shallow fog in the morning on November 24. "The predominant surface wind is likely to be coming from the Northwest direction of Delhi with wind speed 05-08 kmph, mainly clear sky and shallow fog in the morning on November 25." On Sunday, the air quality visibly improved in Delhi after strong surface winds swept through the city, according to the System of Air Quality and Weather Forecasting And Research (SAFAR). It added that the AQI on Wednesday stood at 280 under the 'poor' category. An AQI between zero and 50 is considered 'good'; 51 and 100 'satisfactory'; 101 and 200 'moderate'; 201 and 300 'poor'; 301 and 400 'very poor'; then between 401 and 500 'severe'. The level of PM 2.5 and PM 10 pollutants at 9 a.m. was recorded at 114 (poor) and 220 (moderate), respectively. Meanwhile, Delhi's minimum temperature dipped to 9 degrees Celsius on Wednesday, with India Meteorological Department (IMD) predicting a mainly clear sky throughout the day. The maximum temperature for the day is pegged at 27 degrees Celsius and the relative humidity at 8.30 a.m. was 95 per cent. According to the IMD, Delhi will witness foggy mornings this entire week. /IANS