Delhi continued to battle chilly nights and toxic air on Friday with the minimum temperature dropping to 4.7 degrees Celsius, three notches below the season's normal, and air quality hitting the "very poor" zone.

"Increase in winter chill can be attributed to the fact that there have been no significant changes in the weather pattern across northwestern plains of the country in the past 24 hours. In the wake of this, light and cold northwesterly winds are prevailing over Punjab, Haryana and Delhi region, leading to cold wave conditions in some areas," private weather agency Skymet said.