Severe cold wave is sweeping the northern parts of the country as temperatures plummeted further in the region. Dense fog enveloped several parts affecting road, rail and air services. Visibility dropped to near zero at the Indira Gandhi International Airport in Delhi affecting flight operations badly. This led to delays, diversions and cancellations of around 75 domestic and international flights. The thick cover of fog in Delhi had its cascading effect on the flight operations at the Mumbai airport. Six halt flights between Delhi-Mumbai-Delhi were cancelled and a couple of other flights diverted. An airport official however said, the operation is now returning to normal. In Uttar Pradesh, the early morning fog resulted in the cancelation of some trains by the North Central Railways. In Punjab and Haryana, the minimum temperature dipped at many places, with Narnaul reeling at 1 degree Celsius while heavy fog affected normal life at many places. Ambala, too, came under the influence of piercing chill by registering a low of 2.3 deg C, down by five notches, whileHisar experienced a cold night at 4.6 deg C, down by one degree. In Punjab, icy winds restricted the mercury to 3.4 deg C, down four degrees, while the minimum temperature at Amritsar was 4.1 deg C. The MeT department said, heavy fog reduced visibility early today at Amritsar, Ludhiana and Patiala in Punjab and at Hisar, Karnal, Rohtak and Bhiwani in Haryana. According to reports, normal movement of vehicular traffic was also affected at many places due to fog. Thousands of tourists were left disappointed as Shimla went without a “white” Christmas, but the intense cold wave remains unabated in Himachal Pradesh. The cold wave aggravated in high altitude areas which reeled under minimum temperature ranging between minus 10 and minus 18 degrees Celsius. AIR correspondent Nandini Mittal reports from Shimla that the icy winds blowing, kept the entire state under the grip of biting cold, as mercury further receded in most part of state during last 24 hrs. The Headquarter of Lahaul-Spiti district was recorded season’s lowest today, when mercury plunged to level of minus 8.2 degree Celsius, last night. While, Kalpa in Kinnuar, was at minus three degrees, Buntar in Kullu at minus two degrees. Flights in and out of Himachal Pradesh were badly hit today morning due to heavy fog in Delhi , though Christmas went without snow disappointing many people but now hopes are pinned for a snow fall around new years eve.