Minimum temperature in the city dropped to 12.5 degrees Celsius Thursday, three degrees below normal, and the lowest for the month of October in 26 years, as per the India Meteorological Department (IMD).
The last time the minimum or night time temperature dropped below this mark at the IMD’s Safdarjung observatory, which is representative of Delhi, was on October 31, 1994, when it touched 12.3 degrees Celsius.
Kuldeep Srivastava, head of the IMD’s regional weather forecasting centre in Delhi, said, “The reason behind this is the absence of cloud cover over the city for most part of this month and also calm wind speed. The temperature rises during the day, and at night the heat is radiated back into the atmosphere. A cloud cover acts as a barrier at night time and increases the temperature near the earth’s surface. In the absence of cloud cover, there is rapid cooling at night.”
Minimum temperature in the city has remained between 13.8 and 15 degrees Celsius over the last seven days.
Last year, the withdrawal of monsoon happened on October 10, which meant the city still had some cloud cover until around that date, Srivastava said.
This year, the withdrawal happened on September 30, as a result of which there was little or no cloud cover for most part of October, Srivastava said.
Wind speed also drops significantly after the withdrawal of monsoon. In Delhi, over the last few days, wind speed has remained below 3 kmph between 8 pm and 8 am, which is also helping reduce temperature, Srivastava said.
Maximum or day time temperature also dipped to 30.9 degrees Celsius on Wednesday, but rose to 32.2 degrees Celsius on Thursday.
Srivastava said the drop in day time temperature on Wednesday was because of the haze-like conditions created due to accumulation of pollutants in the air, which impacts solar radiation and reduces temperature near the surface.
The IMD has forecast a drop in temperature in the coming days in Delhi, with minimum temperature expected to be 11-12 degrees Celsius until November 4 and maximum temperature expected to touch 30-32 degrees Celsius.
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