Experts said that extreme temperatures across India are having their worst impact in the country’s teeming megacities, warning that the heat is fast becoming a public health crisis.

India is enduring a crushing heatwave with temperatures in several cities sizzling well over 45°C.

Temperature readings in the capital New Delhi rose into the high 40s on Wednesday, with power usage in the city — where the population is estimated at more than 30 million — surging to a record high.

Indian media reported on Thursday that a labourer in the city had died of heatstroke.

“Cities are more vulnerable to the compounding effects of urbanisation and climate change,” said Aarti Khosla, director at research institute Climate Trends.

“Expect a greater number of hotter days, prolonged dry spells and less rainy days as weather patterns continue to change due to increased human emissions,” she told AFP.

Khosla described heatwaves as “the single largest threat to India’s well-being today”, adding that recent temperatures in Delhi and the surrounding region were “proof that the issue is now about survivability”.

India is no stranger to searing summer temperatures, but years of scientific research have found climate change is causing heatwaves to become longer, more frequent and more intense.

A study published by New Delhi’s Centre for Science and Environment (CSE) this month said Indian cities were not cooling down at night as much as they had in the 2001-2010 decade. It found that the maximum temperature decline was nearly 2°C smaller than previously.

“Hot nights are as dangerous as midday peak temperatures,” it said. “People get little chance to recover from daytime heat slaughter if temperatures remain high overnight, exerting prolonged stress on the body.”

Researchers say human-induced climate change has driven the devastating heat impact in India and should be taken as a warning.

“The suffering India is facing this week is worse because of climate change, caused by burning coal, oil and gas and deforestation,” said Friederike Otto, a climatologist at the Imperial College London and director of World Weather Attribution.

“What we are seeing in India is exactly what scientists said would happen if we didn’t stop heating the planet,” she said.

The world’s most populous nation is the third-biggest emitter of greenhouse gases but has committed to achieve a net zero emissions economy by 2070 — two decades after most of the industrialised West. For now, it is overwhelmingly reliant on coal for power generation.

The government under Prime Minister Narendra Modi, who is seeking a third term, says fossil fuel remains central to meeting India’s rising energy needs and lifting millions out of poverty.