Get ready to face winter chill and dense fog on the eve of the New Year. Delhi's minimum temperature rose to double digits for the first time in 15 days on Friday, but the India Meteorological Department (IMD) said winter chill and dense to very dense fog are  expected to return on the eve of New Year. 

The IMD also issued an advisory saying dense to very dense fog may impact road, train and air traffic in the north west region and there are also chances of tripping of power lines. The IMD also cautioned drivers to be careful while driving or outing through any transport and use fog lights during driving for commuters.

As the Delhi's 24-hour average air quality index stood at 399 on Friday, just two notches below the severe category,  the Centre's air quality panel on Friday directed implementation of curbs under stage III of the Graded Response Action Plan (GRAP) in Delhi-NCR, including a ban on non-essential construction and demolition work.

According to railways, at least 20 trains to Delhi were delayed and three rescheduled due to dense fog in other areas. The IMD) said icy winds from the Himalayas will bring the minimum temperature down by three to five degrees Celsius in the plains of northwest India. "Dense fog is likely to continue over the region during the next 4-5 days. A fresh cold wave spell is likely to commence over northwest India from January 1.

Due to north-westerly winds from Himalayas over plains of northwest India, minimum temperatures very likely to fall gradually by 3 to 5 degree celsius  over the same region during next three days and no significant change thereafter,” the IMD in its bulletin on Friday. Met department officials have stated that cold wave conditions are likely to return to Delhi from January 1 following light rain across the northern plains and fresh snowfall in the mountains under the influence of a western disturbance.

The Safdarjung observatory, Delhi's primary weather station, recorded a minimum temperature of 10.7 degrees Celsius, four notches above the normal. The capital had logged a minimum temperature of seven degrees Celsius on Thursday, 6.3 degrees Celsius on Wednesday, 5.6 degrees on Tuesday and five degrees on Monday. The relief from cold in north India can be attributed to a western disturbance, a weather system characterised by warm moist winds from the Middle East.

With the western disturbance retreating, cold wave and cold day conditions are predicted to wallop parts of Delhi on New Year's eve and the winter chill would intensify further in early January, meteorologists said. The mercury will drop to six degrees Celsius on Saturday and further to four degrees Celsius by Monday (January 2). Dense fog and cold wave conditions are predicted in parts of Delhi from January 1 to 4, according to the India Meteorological Department (IMD) forecast.

A cold day is when the minimum temperature is less than or equal to 10 degrees Celsius below the normal and the maximum temperature is at least 4.5 degrees Celsius below the normal. A severe cold day is when the maximum is 6.5 degrees Celsius or more below the normal.

In the plains, the meteorological office declares a cold wave if the minimum temperature dips to four degrees Celsius or when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches below the normal.

A severe cold wave is when the minimum temperature dips to two degrees Celsius or the departure from the normal is more than 6.4 degrees Celsius.

In its advisory, the IMD said that dense fog contains particulate matter and other pollutants and in case exposed it gets lodged in lungs, clogging them and decreasing their functional capacity which hikes episodes of wheezing, coughing and shortness of breath.