Bone dry March makes Delhi sweat; Met forecasts similar April

Scientists say the sharp rise in mercury, especially in the second half of March, was primarily down to lack of rainfall due to dry westerly winds -- in fact, the city ended the month with zero rainfall for the first time since 2018.

From recording a maximum of 26 degrees Celsius (°C) at the start of the month to a high of 39.6°C on Wednesday, Delhi saw a rise of nearly 14 degrees across the month, ending with an average month maximum temperature of 32.9°C – 2.3 degrees higher than the mean monthly average of 29.6°C.

The high of 39.6°C on Wednesday was the joint second highest single-day March temperature behind 2021, when it touched 40.1°C on March 30. In 1973 too, Delhi recorded a high of 39.6°C on March 29. (Amal KS/HT Photo)

Scientists say the sharp rise in mercury, especially in the second half of March, was primarily down to lack of rainfall due to dry westerly winds -- in fact, the city ended the month with zero rainfall for the first time since 2018. Delhi normally receives 15.9mm of rainfall in March.

And it wasn’t just the days; nights were unusually warm in Delhi in March for a monthly average minimum temperature of 17.6°C -- 2 degrees above the mean monthly normal of 15.6°C.

According to the India Meteorological Department, Delhi’s monthly maximum was the fourth since 1951, behind only 2021 (33.1°C),2004 (33.4°C) and 1953 (34.4°C). The mean minimum temperature is the second highest for March since 1951, behind the 2010 and 1953 which jointly recorded a mean minimum average of 18.5°C. Delhi also saw a rain-less March in 2010, data from the weather office shows.

Safdarjung, which is considered as the base station for Delhi’s weather, recorded four consecutive days of 39 degrees or higher to end the month, with a maximum of 39.°C on Monday, 39.2°C on Tuesday, 39.6°C on Wednesday, and 39.5°C on Thursday.

The high of 39.6°C on Wednesday was the joint second highest single-day March temperature behind 2021, when it touched 40.1°C on March 30. In 1973 too, Delhi recorded a high of 39.6°C on March 29.

“The mean maximum for the month ranks fourth in the last 71 years, but it could have been even higher, had Delhi not been recording a low maximum in the first week. Temperatures in the first week of March were between 25 and 28 degrees, and in the second week touched 32 degrees. It was only in the third week that Delhi crossed the 35-degree mark and the temperature came below it only twice after that,” said Jenamani, adding that a lack of rainfall intensified the summer heat.

“Delhi generally sees three to four western disturbances in March but none of them were active, and therefore, no rainfall was seen in Delhi. We saw wind speeds pick up due to this western disturbances but that only led to a drop in mercury by 1-2 degrees in places, whereas rain can lead to a drop in temperatures by 6 to 8 degrees,” he added.

Other factors included relatively clear skies across Delhi-NCR, and warm westerly winds blowing towards Delhi from Rajasthan, where mercury touched 42°C to 43°C in parts.

Delhi also ended the month with 13 days where the maximum temperature was 35°C degrees or higher. In the second half of the month, it dropped below this mark only on March 22 (34.6°C) and on March 26 (34.5°C). In March 2021, too, the city recorded 13 days where the maximum was 35 degrees or higher.

IMD has now forecast that the maximum will drop by 1-1.5 degrees over the next two days as wind speeds are likely to pick up. Not much relief is expected, however, with temperatures returning close to the 40°C mark by April 3. “Wind speeds will pick up over the next 48 hours, but not much relief is expected. Most stations will hover between 38 and 39 degrees Celsius still,” said RK Jenamani, scientist at IMD.

The weather office’s larger forecast for April, released on Thursday, showed that Delhi-NCR and large parts of the northern plains will continue to record above normal maximum and minimum temperatures, with the forecast for the next seven days showing that the mercury could touch 41°C by April 6 at Safdarjung.

Delhi has been setting weather records every month since August 2020, including a 121-year rainfall record for January after receiving 88.2mm during the month. In February, too, Delhi recorded excess rainfall, receiving 29.7mm, the highest since 2014.

In 2020, several rainfall records were broken -- Delhi received 1,512.4mm of annual rainfall, the second highest ever behind 1,534.3mm in 1933. In May 2021, it got 119.3mm of rainfall in a single day, the highest ever for the month, and in July it got 507.1mm of rainfall, the second highest ever for the city.

In August, Delhi recorded a “very heavy” rainfall spell of 138.8mm in a single day – the highest single for August since 2007. And in September, Delhi recorded 413.3mm of rainfall, an excess of 230%, and the highest for the month since 1944 and the second highest in 121 years.

This wet weather was intertwined with heat records as well -- February 2021 was the second warmest on record, and June recorded ‘severe heatwave’ conditions, with the maximum touching 43.5°C on June 30 — seven degrees above normal.

If the maximum or the minimum has been higher in the last decade as compared to the previous one, it could certainly be due to climate change and man-made influences. There is no doubt that the weather over north India has been particularly erratic over the last two years,” said Dipankar Saha, former head of Central Pollution Control Board’s air laboratory.