At Mohenjo Daro, the 4,500-year-old ruins in Pakistan’s Sindh province, thermometers hit 49°C (120°F) during the last week of May 2024. Across the border in Delhi, the air barely cooled after sunset. And at 10 p.m. on May 30, millions of air conditioners and ceiling fans were still running at full blast when India’s electricity grid hit an all-time peak of 250 gigawatts, according to the Indian Ministry of Power. The grid’s hardest moment did not come at the hottest hour of the day. It came after dark.
The heat wave that blanketed northern India and Pakistan through the second half of May 2024 was punishing by any measure: daytime highs above 49°C, school closures affecting roughly 18 million students in Pakistan’s Punjab province, and hundreds of people treated for heatstroke in hospitals across Sindh and southern Punjab. But what turned a severe weather event into a cascading emergency for more than a billion people was something less visible: nights that refused to cool down.
Nights that never broke
During a typical pre-monsoon heat wave in South Asia, temperatures spike in the early afternoon and then drop enough after sunset for the human body to recover and for electricity demand to ease. This one broke that pattern. The India Meteorological Department’s bulletins through late May documented overnight temperatures in Delhi and across the Indo-Gangetic Plain remaining far above seasonal norms. Pakistan’s Meteorological Department reported districts in Sindh running 4 to 6°C above average, with little relief between dusk and dawn.
The grid data tells the story most clearly. India’s 250 GW record was driven not just by afternoon cooling demand but by thermal generation peaking during non-solar hours. After sundown, when rooftop and utility-scale solar panels stop producing, coal- and gas-fired plants must carry the full electrical load. Normally, falling temperatures reduce that burden within a few hours. In late May 2024, the burden never fell. Air conditioners and fans that would typically cycle down by midnight kept running, stretching the demand curve hours longer than grid operators plan for.
Dense cities made the problem worse. Delhi, Karachi, and Lahore trap heat in concrete and asphalt long after the sun sets, a phenomenon known as the urban heat island effect. When high humidity compounds that retained heat, sweat cannot evaporate efficiently, and the body’s primary cooling mechanism fails. The result is a dangerous feedback loop: people who cannot cool down physiologically depend entirely on mechanical cooling, which loads the grid further.
The human cost, likely undercounted
Pakistan bore some of the most visible consequences. The Punjab provincial government closed schools for a full week, pulling an estimated 18 million students from classrooms, according to Associated Press reporting that cited provincial officials. Hospitals across Sindh and southern Punjab treated hundreds of heatstroke patients. At Mohenjo Daro, where tourists and archaeological workers have little shade, the 49°C reading underscored how extreme conditions had become even in areas far from major urban centers.
In India, the IMD issued repeated heat wave warnings for Delhi and surrounding states, and hospitals in Rajasthan, Uttar Pradesh, and Bihar reported surges in heat-related admissions. But comprehensive casualty figures remain elusive. Rural clinics across both countries often lack the infrastructure to report heat-related illness in real time, and formal attribution of deaths to heat exposure requires post-mortem review that can take weeks or months. The “hundreds treated” figure almost certainly understates the full toll.
The NOAA global climate summary for May 2024 classified the event as a severe and persistent heat wave covering northern and central India along with Pakistan. The Copernicus Climate Change Service’s ERA5 reanalysis confirmed that surface air temperatures across parts of the region reached approximately 50°C, consistent with ground-station readings.
Climate change is loading the dice
South Asia has always experienced brutal pre-monsoon heat. But the frequency and intensity of these events are increasing. A World Weather Attribution rapid analysis of the broader April-May 2024 South Asian heat wave found that climate change made the event significantly more likely and more intense. The study, conducted by an international team of climate scientists, concluded that heat waves of this magnitude are now roughly 30 times more probable than they would have been without human-caused warming.
That finding matters for grid planning. If record-hot nights are becoming more frequent, the assumption that electricity demand peaks sharply in the afternoon and then tapers is outdated. India added more than 18 GW of solar capacity in the fiscal year ending March 2024, but solar generation drops to zero after sunset. The gap between evening demand and available renewable supply is growing, and it is precisely during that gap that the grid is most vulnerable.
Pakistan faces a different version of the same problem. Its grid is smaller, less interconnected, and more dependent on imported fuel. Extended nighttime demand from heat waves compounds existing challenges with load-shedding and transmission losses. The school closures in Punjab were partly a demand-management measure: keeping millions of students home reduced daytime institutional power consumption, but it also signaled that the grid could not absorb the full load.
What the 2026 pre-monsoon season could bring
As of June 2026, the pattern established in 2024 has not reversed. The IMD’s seasonal outlooks for the pre-monsoon period have continued to flag above-normal temperatures across northern India, and Pakistan’s meteorological agency has issued similar guidance. Grid operators in India have been preparing for peak demand scenarios above 260 GW, reflecting both rising temperatures and the rapid spread of air conditioning into middle-class and lower-middle-class households.
The core vulnerability remains the same: solar generation cannot help after dark, and coal plants take hours to ramp up. Battery storage, which could bridge the gap, is still a small fraction of India’s total capacity. Until storage scales up or nighttime demand growth slows, every record-hot night will test the grid in ways that daytime heat alone does not.
For the more than 1.5 billion people living across India and Pakistan, the stakes are not abstract. A grid failure during a nighttime heat wave does not just mean discomfort. When the body cannot cool itself and the power goes out, hospitals lose refrigeration for medications, fans stop in wards full of heatstroke patients, and water pumps shut down. The May 2024 event showed that the system held, barely. The question now is whether it can keep holding as the nights keep getting hotter.
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*This article was researched with the help of AI, with human editors creating the final content.
