Sharp dip in mercury: Delhi to see cold wave in next two days

The Capital’s mercury dipped sharply in the last 24 hours, recording a minimum temperature of 5.5 degrees Celsius (°C) on Sunday morning – two degrees below normal, and almost five degrees less than Saturday’s reading of 10.2°C. The minimum temperature is expected to stay the same for the next two days as well, before cold wave conditions return to the Capital and the mercury dips below 4°C, the India Meteorological Department (IMD) forecast said.

“Cold northwesterly winds are blowing once again, which has led to a drop in minimum temperature, which had risen to 10°C on New Year’s Eve. It could have dipped even further, but cloudy skies prevented cold wave conditions,” said RK Jenamani, scientist at IMD.

Forecast for Monday and Tuesday shows moderate to dense fog is expected in the early hours, with the minimum temperature hovering between 5 and 6°C on both days. Jenamani said a sharp dip in minimum temperature is seen when there are clear skies, and the heat captured during the day is released quickly at night.

“Clouds prevent this heat from escaping and also prevent dense fog formation,” he added, stating similar conditions were expected over the next two days.

From January 4, the IMD has a yellow alert in place for cold wave conditions. The IMD declares a cold wave in a region, when the minimum temperature is 4.5 degrees or more below the normal mark, or when it drops to 4°C or lower. The lowest minimum for any station so far in Delhi has been 3.0°C this season, which was recorded at the Ridge station on December 25, 2022.

Delhi recorded a high of 21.1°C – one degree above normal--on Sunday. The maximum temperature is forecast to hover around the 20-degree mark on both Monday and Tuesday, before dipping to 18°C on Wednesday.

Delhi’s air quality meanwhile continued to improve, dipping down to the ‘poor’ category on Sunday. Delhi’s air quality index (AQI) was recorded as 257 (poor) on Sunday, while it was 337 (very poor) on Saturday.

Forecasts by the Early Warning System (EWS) for Delhi, used by the Commission for Air Quality Management (CAQM) in NCR, shows Delhi’s AQI is likely to return to ‘very poor’ from Monday . “The air quality is likely to deteriorate and reach the ‘very poor’ category on January 2 and 3. The AQI will then improve, but remain in the lower end of the ‘very poor’ category on January 4,” said EWS.

The CAQM had on December 30, 2022, invoked measures under Stage-III or ‘severe’ category of the Graded Response Action Plan (Grap), after Delhi’s AQI had touched 400.