We are now in the second week of December and still, winter chill is not being felt anywhere in the plains of Northwestern and Central India. There are multiple factors for the absence of winter chill. Number one is the frequency and intensity of Western disturbances. We have not seen any active Western disturbance in October and November.
The first week of December has also gone almost dry for the western Himalayas. Due to the absence of Snow cover over the hills, the winds blowing from the Western Himalayas towards the northern plains are not very cold. Moreover, the feeble Western Disturbance is instrumental in altering the wind pattern. The normal flow of northerly winds is obstructed time and again due to the feeble Western disturbance.
Another factor is the lack of rain activities over North and Northwest India. Winter rains help in reducing the temperature and increasing the moisture. Due to the low temperature and increased moisture, moderate to dense fog appears over Northern Plains leading to a significant drop in day temperatures, which we have not seen until now.
Pollution is another factor, especially for Delhi-NCR and all the big cities. The pollutants trap the heat of the Sun and do not allow the temperature to drop. There may be a marginal fall in day and night temperatures during the next few days over Northwest and Central India but we do not expect a steep fall for at least during the next one week.