New Delhi, Dec 30 : A thick layer of fog covered the national capital on Saturday morning disrupting rail, airline and traffic movement. However, the city's minimum temperature settled at 11.8 degree Celsius, five notches above the seasonal average, the India Meteorological Department (IMD) said. The IMD said that dense to very dense fog conditions are very likely to continue in most places over Punjab, Haryana, Chandigarh and Delhi till Sunday morning and in some pockets for subsequent three days. 'Delhi's Palam station recorded 700 m and Safdarjung 400 m visibility at 9 a.m.,' said the weatherman. The IMD classifies fog intensity into four types -- shallow, moderate, dense and very dense fog. The visibility ranges from 999 m to 500 m, 499 m to 200 m, 199 m to 50 m and < 50 m, respectively. As the day unfolds, the fog is forecasted to gradually dissipate, revealing a clearer atmosphere by the afternoon while the maximum temperature is expected to hover around 19 degree Celsius. Due to fog, flight and train schedules are also being affected, with many flights experiencing delays and some possibly facing cancellations. In the early hours of Saturday, over 70 international and domestic flights arrival and departure faced hours of delays, owing to low visibility. In a fog-induced challenge for commuters, several trains arriving in the Delhi region are also dealing with delays, causing frustration among passengers. According to Railways, a total of 30 trains including Jammu Tawi- New Delhi Rajdhani Express, Mumbai- Nizamuddin August Kranti Rajdhani, Ayodhya Dham- Delhi Jn Express were delayed by hours. Delhi's air quality remained in the 'severe' category. At the Anand Vihar area, PM2.5 levels remained into the 'severe' category standing at 429 and PM10 reached 414, and CO was at 107, or 'moderate', according to the Central Pollution Control Board (CPCB). The Air Quality Index (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'; and 401 and 500 'severe'. The Indira Gandhi International (IGI) Airport T3 witnessed PM2.5 level at 361, in the 'very poor' category and PM10 at 251, under the 'poor' levels. /IANS