New Delhi, Jan 25 : Delhiiites woke up to dense fog and chilly morning with minimum temperature at 4.8 degree Celsius, three notches below the seasonal average, according to the India Meteorological Department (IMD). The IMD's forecast showed that the maximum temperature on Thursday is likely to hover around 19 degrees Celisus, and said that it is going to be a "partly cloudy sky". The IMD said that due to fog the visibility at Delhi-Palam was reduced to 25 metres and 50 m at Safdarjung at 5:30 a.m. disrupting flight and train operations. Several flights and trains were reported delayed owing to bad weather conditions. Moreover, the air quality continued to remain in the 'very poor' category at several stations across the city. In the Anand Vihar area, at 9 a.m., PM2.5 levels were recorded to be in the 'very poor' category standing at 304 and PM10 reached 166 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 IGI Airport T3 witnessed PM2.5 levels at 156, and PM10 was at 113, both falling under the 'moderate' category, respectively. /IANS