With the mercury dropping to 13.7 degrees Celsius, the national capital on Tuesday experienced its coldest October night in 11 years. The temperature was recorded four degrees below the season's normal. The maximum temperature was tracked at 33.8 degrees Celsius.
As per records available with the Safdarjung observatory, it was last in 2009, on October 26 and October 28, when the mercury plummeted to 13.5 degrees Celsius. In the Palam observatory, the maximum temperature was recorded at 33.3 degrees Celsius and the minimum temperature was 17.1 degrees Celsius, a notch below the season's normal.
According to Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, the wind speed remained high on Tuesday, around 15-16kmph, from the north-westerly direction. The northern component in the wind usually lowers the minimum temperature, Srivastava said.
Srivastava said while the AQI is likely to remain in the same range on Wednesday, the wind direction over Delhi is likely to change to north-easterly from Thursday. The change in direction is likely to reduce wind speed and deteriorate air quality.
Why the dip in temperature
According to scientists, the night sky has been clear over the past few days. They also say that the wind at night becomes calm, with its speed dropping to almost zero. Scientists at the IMD believe that these two factors result in higher radiation from the Earth's surface at night time which cools the surface and the air close to it, a report in the the Indian Express said.