New Delhi: The national capital came under the grip of the chilly winters as the mercury dipped below 4 degrees Celsius in the National Capital Region (NCR) on Thursday, the coldest day recorded in 2018. Himachal Pradesh's capital Shimla also reeled under the cold wave with temperatures dipping to 6 degree Celsius. The weather office has predicted a further dip in temperature over the next two days.

The sudden dip in temperature is due to the cold wave conditions prevailing over northwest India, the MeT Department said, adding that the temperature is likely to fall further till December 22.

The maximum temperature was 22.3 degree Celsius, normal for this time of the year. The minimum, however, was four notches below the season's average. Minimum temperature in December dipped to Thursday's level last in 2014. The humidity oscillated between 100 and 42 per cent.

According to the government-run System of Air Quality and Weather Forecasting And Research (SAFAR), the overall air quality index of Delhi continues to be "very poor" at 319.

If the air quality index is in the range of 51 to 100, it is considered satisfactory; 101-200 is moderate and 201-300 falls under the category of poor. 300-400 is considered 'very poor' and 401-500 falls under the category 'hazardous'.

The Met office has forecast clear skies for Friday along with moderate fog in the morning and haze and smoke thereafter.

Thursday saw cold wave conditions intensify in Kashmir as the minimum temperature dropped at most places and residents in some areas of the city reported freezing of water supply lines.

The night temperature dipped drastically in Leh district of Ladakh region as the mercury plunged nearly nine degrees Wednesday, the Met Department said. The mercury fell from minus 6 degrees Celsius on the previous night to minus 14.7 degrees Celsius, a Met official said.