Delhi experienced its coldest day in five years as the minimum temperature dropped to 2.9ºC, five degrees below average, early on Christmas day on Sunday.The dense fog in the morning disrupted train services but flights were not affected. “There is a heavy backlog in trains, leading to many delays and rescheduling of trains,” a Northern Railways spokesperson said.“As many as 30 trains were running late and 10 services were rescheduled in the capital, where dense fog reduced visibility to 400 metres in the morning,” the official said.He added that as a precautionary measure, 31 long distance trains have been cancelled till Jan.31 and 27 suburban trains have been cancelled till Dec.31 due to dense fog that prevails in the region during this period.A Delhi International Airport Ltd (DIAL) spokesman said that no flights had been affected on Sunday. The weatherman has predicted the chill and fog to prevail in the days ahead. “The chill and fog will prevail in the days ahead. The cold north-westerly winds from the Himalayas coupled with the heavy fog cover that obstructed the sunrays are causing this chill,” an official at the India Meteorological department (IMD) said.