New Delhi, Jan 23 : Delhi on Tuesday recorded 6.1 degrees Celsius minimum temperature, one notch below the seasonal average, the India Meteorological Department (IMD) said. According to IMD's forecast, the maximum temperature in the national capital is likely to hover around 18 degrees Celsius. The IMD said that due to fog, visibility at Delhi-Palam reduced to 200 metres at 7 a.m. to 250 m at 9.30 a.m. while at Safdarjung, it was at 500 metres. Owing to low visibility, 28 trains were reported running late from one to three hours, according to Indian Railways. 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 344 and PM10 reached 235 or 'poor', 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 209, and PM10 was at 121, both falling under the 'poor' and 'moderate' category, respectively. /IANS