Mercury below 20°C in Delhi, first time this season
The Met department has forecast that the minimum temperature will remain between 18°C and 19°C till Friday
Cold northwesterly winds and clear skies helped push Delhi’s minimum temperature below 20 degrees Celsius (°C) for the first time this season, said the India Meteorological Department (IMD).
Safdarjung, the city’s base weather station, recorded a low of 18.3°C — four degrees below normal for this time of the year and the earliest the Capital’s minimum temperature has plunged below 20°C in at least a decade. The Ridge station in north Delhi recorded the lowest minimum of 16.5°C.
Temperatures in the city started dipping after monsoon’s withdrawal on September 30, when the night temperature was 22.6°C. The minimum fell to 22.1°C on October 1 and 20.1°C the day after that. IMD data since 2013 shows that last year, the minimum temperature fell below the 20°C mark on October 9. The year before that, it happened on October 14. In 2019 and 2020, it fell below 20°C on October 4. In 2013, the minimum temperature fell below 20°C on October 19, data showed. Data from before 2013 was not immediately available.
IMD has forecast that the minimum temperature will remain between 18°C and 19°C till Friday, before warmer winds briefly push the temperature to 21-22°C on the weekend. “The withdrawal of the southwest monsoon was declared on September 30 and from October 1, we have seen a dip in night-time temperature. This is because the moisture in the air has vanished, leading to clear skies, that allows faster heating during the day, but at the same time, this heat is lost fairly quickly at night as there are no clouds to trap the heat,” said Kuldeep Srivastava, scientist at IMD.
He said the withdrawal of the monsoon also leads to the wind direction changing to northwesterly, which are colder, drier winds. “These winds are leading to that night-time nip in the air,” Srivastava added.
The daytime temperature in Delhi, meanwhile, was 34.4°C, around the normal mark.
While the wind direction has changed, it was yet to significantly impact Delhi’s air quality with the smoke it carries from the annual practice of stubble burning in the neighbouring states of Punjab and Haryana. On Tuesday, Delhi’s air quality remained “moderate”, but deteriorated slightly in comparison to Monday. The air quality index was recorded at 155 on Tuesday against Monday’s 147.
However, low temperatures also tend to negatively influence air quality by slowing down the dispersal of pollutants.
In Punjab, the daily farm fire count remained over 100 for the third consecutive day at 105 on Tuesday, data from the Indian Agricultural Research Institute (IARI) showed.
According to Gufran Beig, founder project Director at the System of Air Quality and Weather Forecasting And Research (Safar), Delhi can be impacted by the farm fires, depending on the meteorological conditions. “Strong northwesterly winds can bring these pollutants towards Delhi. At the same time, dipping temperature makes the atmosphere more stable and can trap this smoke locally. However, if there are strong local winds in Delhi too, this pollution too can disperse immediately,” he said.