Delhi's minimum temperature rose to double digits for the first time in 15 days on Friday, but the respite is predicted to end soon.
The India Meteorological Department (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," it said in a statement.
The Safdarjung observatory, Delhi's primary weather station, recorded a minimum temperature of 10.7 degrees Celsius, four notches above the normal. It was also the highest minimum temperature this month. The maximum temperature settled at 22.8 degrees Celsius, a departure of 2 degrees Celsius from normal.
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 by Saturday, cold wave and cold day conditions are predicted to wallop parts of Delhi in early January, meteorologists said. The mercury will drop to eight 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 5, according to the IMD.
A cold day is when the minimum temperature is less than or equal to 10 degrees Celsius below normal and the maximum temperature is at least 4.5 degrees Celsius below normal. A severe cold day is when the maximum is 6.5 degrees Celsius or more below the normal. According to the IMD, 'very dense' fog is when visibility is between 0 and 50 metres, 51 and 200 metres is 'dense', 201 and 500 metres 'moderate', and 501 and 1,000 metres 'shallow'.
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.
