From heatwaves to rainfall records:An extreme July for Delhi’s weather | Latest News Delhi - Hindustan Times
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From heatwaves to rainfall records:An extreme July for Delhi’s weather

By, New Delhi
Aug 02, 2021 08:18 AM IST

Data from the India Meteorological Department (IMD) shows that till July 29, Delhi recorded 463.5mm rainfall. In an average year, this number is 210.6mm. The last time there was more rain than this in July was in 2003 when the city recorded 632.2mm.

July is turning out to be a month of weather extremes in Delhi, scientists and independent weather experts said, recounting temperature and rainfall readings from that show that the first half of the month was unusually hot, before the tail end of turned uncharacteristically wet.

The city has been breaking a weather record every month since August 2020. PREMIUM
The city has been breaking a weather record every month since August 2020.

The city has been breaking a weather record every month since August 2020. For instance, this February was the second warmest in 120 years, with the mean maximum temperature in the month touching 27.9 degrees Celsius, falling marginally short of the all-time record of 29.7 degrees Celsius in 2006.

Then March this year recorded the hottest day in 76 years, with the mercury levels touching 40.1°C on March 29.

But then, after a sweltering February and March, the conditions changed again in April and the lowest minimum temperature in at least a decade was recorded on April 4, at 11.7°C.


July 2021 has kept with the record-breaking pattern: it started off with an unusually hot day when the maximum spiked to 43°C. Over the next eight days, there were four heatwave days – a frequency not seen since 2014. Around this time, the monsoon should have arrived – but it would not till nearly the middle of the month on July 13, which was the latest onset since 2013. And in a span of three weeks, the monsoon has now dumped more rain this month than it did in any year since 2003.

Data from the India Meteorological Department (IMD) shows that till July 29, Delhi recorded 463.5mm rainfall. In an average year, this number is 210.6mm. The last time there was more rain than this in July was in 2003 when the city recorded 632.2mm.

With two days remaining, the city may break this record, according predictions of moderate to heavy showers by IMD officials.

The trend of aberrant weather patterns continues in another area: most of the rain the city has received this year is a result of short and intense showers, concentrated over just a few hours a day. “This could be an impact of climate change,” said Kuldeep Srivastava, head of IMD’s regional weather forecasting centre.

Srivastava said over the last few years, Delhi has recorded more frequent spells of short and intense showers, instead of uniform and more evenly distributed rains. “We have been studying this trend for the past few years. Earlier, we used to see that rainfall of 100mm would be uniformly distributed over several days in normal monsoon months.”

Mahesh Palawat, vice-president (meteorology and climate change) at Skymet Weather, a private weather forecasting agency, said that though it is not new for July to record high temperatures or heavy rain, it is rare for the same month to start off with heatwave recordings and then suddenly change gears to record intense showers.

For instance, Delhi recorded six heatwave days in July 2012, but received just 94.8mm of rain the entire month, said Palawat.

“When July started off this year, the monsoon was delayed and temperatures were high, because of westerly winds,” he added.

In another odd weather occurrence this season, northwest India, including Delhi, saw a ‘break monsoon’ even before the onset of monsoon. A monsoon break is a period when it goes into a recession of a week or more.

Scientists said that a break monsoon in this region is usually seen in August, when parts of Delhi and the National Capital Region (NCR) have already received some showers.

“Climatologically, break monsoon conditions are more frequent in August. That was the climatological behaviour of the monsoon. This time, such a situation happened by the end of June itself and continued till mid July, and we experienced heatwave days in parts of northwest India,” a Met official said.

The sudden change from hot and sultry to rainy played out not just over days but at times over a few hours. For instance, on July 27, Delhi’s Safdarjung recorded 100mm rainfall. But, Met officials said that instead of being evenly distributed throughout the day, this was concentrated in just three hours, between 5.30am and 8.30am.

Srivastava added that this trend has been affecting the number of rainy days (rainfall above 0.16mm) recorded every month, and is also causing more discomfort on days when the city does not receive rain.

“Earlier, with the rain being more evenly distributed and the city having more open spaces, the water would slowly seep into the ground. This would also cause the ground to cool and result in low temperatures for a few days after rain. Now, the rainwater just runs off and the cooling effect is much lower. Besides, with longer dry spells, the mercury goes up, resulting in higher temperatures,” Srivastava said.

Palawat agreed and explained that July and August are the wettest months in Delhi, which receives nearly 60% of a season’s rainfall during this period. This time, he said, despite the delayed onset of monsoon, the weather systems have been favourable for heavy rain.

“This time the monsoon was delayed by 16 days, but after that two low-pressure areas formed in the North Bay of Bengal, which travelled towards Delhi. Over the last few years, we have seen that the low-pressure areas that form over the Bay of Bengal usually travel in the westerly direction, so its impact is not felt in Delhi as much. This time, it has travelled in the northwest direction and come very close to Delhi and has created favourable conditions for rains here,” he said.

Other Met scientists, however, said such extreme weather events were seen globally this year, but can be called a “trend” only if such events are recurrent and consistent over the next few years as well.

“It might be too early to say that such weather events are happening because of the impact of climate change. More studies need to be carried out, and weather patterns need to be studied across the world more closely to establish that,” a senior official at the weather office said, asking not to be named.

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  • ABOUT THE AUTHOR
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    Soumya Pillai covers environment and traffic in Delhi. A journalist for three years, she has grown up in and with Delhi, which is often reflected in the stories she does about life in the city. She also enjoys writing on social innovations.

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