A moderate fog cover over the national capital region disrupted train and flight operations as visibility dropped to 300 metres on Friday.Operations at the Indira Gandhi International (IGI) Airport here were affected due to the low visibility and at least 15 flights were delayed. The Railways had to cancel 18 trains while 62 were delayed besides 20 rescheduled due to fog in several parts of northern India. The minimum temperature was recorded at 7.2 degrees Celsius, the season's average. The maximum was likely to hover around 20 degrees.The sky will remain clear during the day, an India Meteorological Department official said. The visibility which had dropped to 300 metres at 5.30 a.m., improved to 600 metres at 8.30 a.m., while the humidity was 97 per cent.Thursday's maximum temperature settled at 20.3 degrees Celsius, one notch above the season's average while the minimum was recorded at five degrees Celsius, two notches below the season's average.