For one day in late April, all of the world’s 50 hottest cities were in India as the country experienced an extraordinarily severe heatwave.

Air-quality monitoring platform AQI said that there was “no modern precedent” for this occurrence and that it was “not normal”.

“This is not a normal April,” the platform said. “And it demands a serious, data-grounded reckoning.”

“On April 27, something that has no modern precedent happened across global weather data. When AQI compiled its daily heat index, every single one of the world’s top hottest cities was located inside India,” it explained. “Not one entry from the Middle East. Not one from sub-Saharan Africa. Not one from Australia. India occupied the entire list, from rank 1 to rank 50.”

Across the 50 cities, the average peak temperature that day was 44.7C. Even the coolest maximum on the list – Solapur at 41.9C – “would be considered a public health emergency anywhere in Europe”, the platform noted.

At 46.2C, Banda in the northern state of Uttar Pradesh recorded the world’s highest temperature that day. Even night-time temperatures stayed dangerously high.

Most of the 50 hottest cities were concentrated in the “interior heat belt”, including Uttar Pradesh, Madhya Pradesh, Maharashtra, and Rajasthan.

According to climatologist and weather historian Maximiliano Herrera, the extreme heatwave was “among the top if not the top harshest for April, which is usually not the hottest month of the year”.

He told CNN that dozens, “if not hundreds”, of April heat records were shattered.

Scientists link the worsening heat to the climate crisis, noting that Indian summers are arriving earlier and getting more intense. Experts warn that by 2050, parts of India could experience heat beyond the survivability limit for humans.

AQI says this “is an emergency health signal”.

“When 50 cities share average temperatures above 37.5C – core human body temperature – entire regions are living in conditions where heat-related illness becomes a mass public health risk,” it said.

“April heatwaves of this intensity across this many cities simultaneously are not historically typical of the Indian subcontinent. India has always had hot summers. But the geographic spread, the duration, and the concurrence of multiple regions crossing extreme thresholds on the same day have all been intensifying.”

Concerns are growing that the coming summer could get worse. India is also facing fuel shortages due to the supply-chain disruption caused by the US-Israeli war on Iran, making it harder to meet its rising cooling demands.

To make matters worse, the Indian Meteorological Department has predicted below-average monsoon rains this year, increasing the chances of drought.