New Delhi, Dec 14 : The national capital saw a massive dip in the mercury on Monday and if the weatherman is right it may plummet further by Thursday-Friday, the India Meteorological Department (IMD) said. Delhi recorded a minimum temperature of 8.4 degrees Celsius, down from 11.4 on Sunday and 14.4 on Saturday. "The temperature has dropped by six notches as compared to Saturday," head of the IMD's regional forecasting centre, Kuldeep Srivastava told IANS. Nationwide, there will be a fall in minimum temperatures by 3-5 degrees Celsius over most parts of northwest India during next four days till Friday. There will be, however, no significant change in minimum temperatures over most parts of central and east India. Dense fog will form its blanket over Jammu division, Uttarakhand, Punjab, Haryana, Chandigarh, Rajasthan, Uttar Pradesh, Bihar, Sub-Himalayan West Bengal, Sikkim, Assam, Meghalaya and Tripura. Under the influence of strengthening of the easterly wave, scattered to fairly widespread rain and thundershowers are expected over Tamil Nadu, Puducherry, Karaikal, Kerala, Mahe and Lakshadweep area from Wednesday to Friday. The Safdarjung Observatory, which provides the representative data for the city, recorded a minimum temperature of 8.4 degrees Celsius, while Lodhi Road Observatory recorded it at 7.4 degrees Celsius, according to the data provided by the weather forecasting agency. "The temperature will dip further on December 17-18. There will be shallow fog and sky will be clear during the day. No rainfall is expected in the coming days," the senior IMD official added. Delhi's air quality was recorded in the "moderate" category on Monday due to favourable wind speed. The city's air quality index (AQI) was 165 at noon. On Sunday, the average 24-hour AQI in the national Capital stood at 305 in the "very poor" category. Union Ministry of Earth Science's air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (SAFAR), said that the air quality is better as high winds helped to clean accumulated pollutants. The AQI is likely to marginally deteriorate from the moderate to the poor category in the next two days. /IANS