A 'Day Colder than Shimla,' Now Incessant Rains: What's Happening in Bengaluru?

Experts tell us why Bengaluru has been making headlines for the past few days with its weather patterns.

On Thursday, 12 May, Karnataka's capital Bengaluru recorded its second coldest day in the month of May in 50 years.

(Photo Courtesy: Twitter/@WeatherIndia)

Just a few days before it saw incessant rains that has led to flooding in several parts, Bengaluru, on 12 May, recorded its coldest day in the month of May in 50 years as the maximum temperature plunged to 23 degrees Celsius.

This occurrence, paired with the severe heatwaves that have gripped parts of north India, led to a strange situation – Bengaluru was colder than many of India's hill stations on 12 May.

On 12 May, heatwave gripped northern states of India. Pahalgam's maximum temperature was 24.3 degrees, followed by Mahabaleshwar (24.8 degrees), Mukteshwar (25.1 degrees), Kalimpong (26.4 degrees), Shimla (26.6 degrees), and Srinagar (28.8 degrees).

Here's why this happened.

2021’s La Niña Is Partly Responsible

Bengaluru's maximum temperature fell a staggering nine degrees between 9 and 10 May, from around 33 degrees to 24 degrees Celsius.

Two days later it hit 23, marking the coldest May day in half a century. The last time the city had recorded a colder May day was on 14 May, 1972, when its maximum temperature was reported to be 22.2 degrees.

The drastic temperature-drop appears to be the work of weather systems, including a low pressure area forming in the Bay of Bengal coastal area.

Dr Raghu Murtugudde, an earth system scientist who teaches at the University of Maryland, said that the unusual weather events were partly due to the La Niña, a weather pattern that occurs in the Pacific Ocean every few years.

"The La Niña of 2021 had set up a north-south pressure pattern that had pushed cold air far south into peninsular India. This is expected during a La Niña," he said.

"The La Niña enables cooling over Bengaluru and south as usual but with colder temps. A few years ago a similar La Niña winter had produced frost over Mahabaleshwar and Ooti I think."

Dr Raghu Murtugudde

Bengaluru is also witnessing its wettest May in the last 10 years. At least two people were killed in Bengaluru on Wednesday, 18 May, and several scrambled for shelter as heavy rains caused widespread waterlogging across the city.

"A cyclonic circulation in coastal and south interior Karnataka and moderate humid winds from Arabian sea are feeding moisture over Karnataka, including Bengaluru," Skymet official Mahesh Palawat told The Quint.

The rains are expected to continue for the next few days, as monsoon advances into the Bay of Bengal. "Now cyclones are dragging the monsoon trough forward and creating favorable monsoon onset conditions," Dr Murtugudde said.

The North Grapples with Heatwaves

Meanwhile, parts of north India have been struggling with intense heatwaves since March, leading to warmer temperatures in hill stations.

Areas in Delhi and Uttar Pradesh experienced temperatures around 49 degree Celsius. Such conditions are expected to persist in Rajasthan, south Punjab, south Haryana and Madhya Pradesh on 20 May.

Like the unusually cold weather in Karnataka, the north Indian heatwaves are also the result of weather systems but these seem to have been altered due to climate change.

"The unusual thing was that the winds from the west created early heatwaves which also extended much further south due to the La Niña pressure pattern."

Dr Raghu Murtugudde

"So a combination of global warming impact on heatwaves combined with the natural variability of La Niña produced freak patterns," Dr Murtugudde told The Quint.

Furthermore, storms originating in the Mediterranean region led to less pre-monsoon rainfall in north-western and central India and a high pressure area caused hot and dry weather, Naresh Kumar, a senior scientist at IMD told the BBC.

The coal crisis, paired with an increase in power consumption, has made matters worse.

“The fact that we have blundered into extreme heat waves, the first of its kind in 120 years, is no coincidence. Scientific studies have shown that global surface temperatures have increased by 1.1degrees since pre-industrial levels," Aarti Khosla, Director, Climate Trends, told The Quint.

"More heat, and associated greater power demand has created a power crisis, which is in reality the poor planning with regards to transporting coal and transmitting power. It is not a shortage of coal," she added.

(With inputs from BBC)