From heatwaves to rainfall records: An extreme July for Delhi’s weather

NEW DELHI: 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. 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.

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.