New Delhi, Dec 30 (PTI) A cold wave swept through Delhi on Wednesday as the minimum temperature dipped to 3.5 degrees Celsius, the India Meteorological Department said.
It is likely to get even colder on New Year's Eve, it predicted, as dry and icy winds barreled through the plains. The Safdarjung Observatory, which provides representative data for the city, recorded a minimum of 3.5 degrees Celsius and a maximum of 16.4 degrees Celsius.
On December 18, Delhi had recorded a maximum of 15.2 degrees Celsius, the lowest so far this season. The weather stations at Jafarpur and Lodhi Road recorded a low of 3.5 degrees Celsius and 3.7 degrees Celsius, respectively, it said.
During nighttime, "dense" fog reduced visibility to 50 meters in the Palam area. However, it improved to 400 meters by 9 am. The visibility at Safdarjung was 500 meters.
According to the IMD, "very dense" fog is when visibility is between 0 and 50 meters, 51 and 200 is "dense", 201 and 500 "moderate", and 501 and 1,000 meters "shallow".
In the plains, the IMD declares a cold wave if the minimum temperature dips to 4 degrees Celsius. A severe cold wave is when the minimum is 2 degrees Celsius or less. Cold wave conditions are predicted in parts of the city over the next two days, it said.
Kuldeep Srivastava, the head of the regional forecasting centre of the IMD, said cold and dry northerly/northwesterly winds from the western Himalayas have been barreling through the plains, bringing the minimum temperature in north India down.
According to IMD, a cold wave is also declared when the minimum temperature is 10 degrees Celsius or below and is 4.5 notches less than normal. A "severe" cold wave is when the minimum temperature dips to two degrees Celsius or the departure is more than 6.4 degrees Celsius. On December 20, the Safdarjung Observatory recorded a minimum of 3.4 degrees Celsius, the lowest this season so far.
The mean minimum temperature (7.06 degrees Celsius) in December this year so far is less than last year when it was 7.6 degrees Celsius. Last year, the national capital broke the record of the longest cold spell, registering 18 consecutive cold days.
At 9.4 degrees Celsius, Delhi had also recorded the lowest maximum temperature in December in 119 years.
This year, however, the city has witnessed only three "cold" days and 7 "cold wave" days so far.
A cold day is declared when the maximum temperature is less than or equal to 16 degrees Celsius.
Delhi's air quality was recorded in the "poor" category on Wednesday. The city's 24-hour average air quality index (AQI) was 290. It was 265 on Tuesday, 253 on Monday, 396 on Sunday, 337 on Saturday, 357 on Friday and 423 on Thursday.
An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe".
Officials at the India Meteorological Department (IMD) said favourable wind speed, upto 15 kmph, aided in dispersion of pollutants.