For the past four days, Chennai has been experiencing a chill weather in the nights and warm mornings. The minimum temperature dropped by one or two degree Celsius, making the nights colder in the city and suburbs.

On Thursday, Nungambakkam and Meenambakkam recorded a minimum temperature of 18.7 degree Celsius and 19.2 degree Celsius against the average of 21 degree Celsius.

N. Selva Kumar, a resident of K.K.Nagar, said, “I wear winter clothes even if I have to travel around 8 a.m. as it is quite cold for the past few days. Though it is sunny, it gets warm only around 8.30 a.m.” Residents said it is not easy for those staying out after 9 p.m. as nights are getting colder.

Officials of the Meteorological Department said that clear sky leads to the rise in maximum temperature and dip in the minimum temperature. It allows more solar radiation during the day and emission of radiation from earth surface during nights. When the sky is cloudy, the outgoing radiation from the earth is less which keeps the weather warm.

The maximum temperature has been one or two degree Celsius above the average of 30 degree Celsius in the city since Monday.

Y.E.A.Raj, Deputy Director General of Meteorology, Regional Meteorological Centre, Chennai, said strong land breeze that develops at 4 a.m. and brings cold air also contributes to the dip in the minimum temperature.

The coldest temperature level in a day is recorded half an hour to one hour after the sunrise when the incoming radiation just begins and the remaining earth radiation gets exhausted, he said.

In coastal areas, including Chennai, the minimum temperature did not dip as much as in places such as Vellore and Tirupattur that recorded 13 degree Celsius and 14 degree Celsius, which was about 5 degrees less than the average, respectively on Thursday.

There is more moisture in the atmosphere in the coastal localities, which does not allow the nights to get colder, he added. Last year, the city registered the lowest minimum temperature of 19 degree Celsius on February 3 and in 2009, the lowest temperature was 18.6 degree Celsius on February 11.

The Meteorological Department registered an all-time lowest temperature of 16.2 degree Celsius on February 3, 1982.

This year's winter has started on a slightly warm note as the monthly mean temperature has deviated by 0.5 degree Celsius from the average of 20.9 degree Celsius in January, he said.

The nights would continue to be cool for the next two days with the minimum temperature expected to be around 19 degree Celsius, he added.

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