A heavy blanket of fog engulfed the national capital region on Tuesday with the visibility dropping to 300 metres. At least 21 trains were cancelled and 64 delayed due to fog."The sky will remain clear during during the day, with dense fog in the morning," an official of the India Meteorological Department (IMD) said. The minimum temperature was recorded at 8.4 degrees Celsius, a notch above the season's average. Meanwhile, 24 trains have been rescheduled due to fog in several parts of northern India. The maximum temperature is likely to hover around 21 degrees Celsius.The humidity at 8.30 a.m. was 97 per cent and the visibility was 300 meters.Monday's maximum temperature settled at 20.1 degrees Celsius, one notch above the season's average while the minimum was recorded at 5.7 degrees Celsius, a notch below the season's average.