The climate of Delhi is an overlap between Monsoon-influenced humid subtropical and semi-arid classification, with high variation between summer and winter temperatures and precipitation.
Winter arrives in Delhi by late November or early December. Minimum temperatures gradually enter single digits by this time of the year, while days are pleasant. Though usually not cold initially, December suddenly becomes cold in the latter half, as chilly north-westerly winds from the Himalayas begin sweeping the Northern Plains. There can be some exceptions when maximum temperatures drop down to single digits whereas most of the time they will hover around 20°C or so.
Talking meteorologically, Cold Day condition is when the maximum temperature is 16°C or below. Such drop in temperature is generally observed during December and January. However, there is no such official bound for the same. Even February can witness temperatures around 16°C or below, on very rare occasions. However, such Cold Day conditions are mostly confined to January and February. The average monthly day temperature for Delhi for the month of December is 23.1°C and in January, it dips to 20.5°C. This is the lowest average monthly temperature.
There are many factors which are held responsible for Cold Day conditions. Two of the most prominent conditions are persistent thick cover of cloud lasting for a prolonged period. Secondly, it is the thick envelope of dense to very dense fog which should persist till noon hours.
Even rains are held responsible for Cold Day conditions, but then when there is no rain, thick amount of cloud cover teamed up with gentle breeze of 10-15kmph, also results in Cold Day conditions. Contrary to this, when the sky is clear with bright sunshine , Cold Day condition seems to be a usual no.
As per the records, there have been years when we have had successive nine cold days in the month of January in 2011 and 2013. In 2013, continuous spell of Cold Days was from January 1-9 and the lowest maximum temperature was 9.8°C, recorded on January 3. In 2011, continuous spell of Cold Days was from January 3-11 and the lowest maximum temperature being recorded at 11°C on January 10.
Frequency, intensity and duration of Weather Systems play a major role in governing Cold Day conditions.
We have been witnessing Cold Day conditions every year barring 2018 and till date we haven’t seen any Cold Day so far. As per Skymet Weather, no such condition is favourable in the coming week as well, which means by mid of January also we don’t expect Cold Day conditions to happen anytime soon.
Image Credit: Skymet/ The Pioneer
Please Note: Any information picked from here must be attributed to skymetweather.com