Clear skies and cool northwesterly dry winds over Delhi NCR is making national capital colder than many districts of Himachal Pradesh. In fact, the month of October this year was the coldest in the last 58 years for Delhi. The mean minimum temperature of October for Delhi this year was 17.2 degree. It was the lowest temperature recorded since 1962 when it was 16.9 degrees.
The month of November commenced with the record low temperature of 11.4 degrees which was lowest in the last decade for November 1. Since then the minimum for Delhi is dropping. Today, Delhi has recorded the minimum temperature of 10 degrees, equal to the minimum temperature of Shimla in Himachal Pradesh. Whereas, the minimum temperature of Shimla Airport is higher than Delhi with 11.4 degrees. Minimums of Dalhousie, Kangra, Dharamshala, and Kasauli are also more than Delhi. All the above-mentioned cities are hill destination, famous for chilly winters.
The reason for higher minimum temperatures of Himachal Pradesh can be attributed to the cyclonic circulation which is over North Pakistan and adjoining Punjab and Himachal Pradesh. This is leading to a change in wind direction from north-west to southeasterly and easterly. The sky condition is also partly cloudy to cloudy during the night. The energy emitted by the earth during the night in the form of longwave radiation which gets trapped between the surface of earth and clouds leading to a rise in night temperatures. This is known as the greenhouse effect.