Heat index crosses 50°C in monsoon, peak power demand soars: CSE

The analysis found that during the monsoon period, Delhi’s daytime and nighttime land surface temperatures soared by about 2.1°C and 3°C respectively compared to 2024.

Delhi recorded unusually high heat index levels this monsoon, driven by elevated humidity despite relatively lower temperatures, leading to a surge in power demand, according to an analysis by the Centre for Science and Environment (CSE) released on Monday. The study found that 67% of the variation in Delhi’s daily peak electricity demand is now attributable to the combined impact of heat index and cooling needs.

Power demand data underscored the sharp escalation. Peak demand rose by 567 MW, a 10.4% increase, from March to April 2025 (HT Archive)

While the pre-monsoon months of March to May registered moderate heat index values of around 31 to 32°C and relatively stable power use, the monsoon months of June to August saw a dramatic spike, with the index crossing the 46 to 50°C mark. This surge in “felt” temperature coincided with record-breaking electricity use, the report stated.

CSE’s executive director for research and advocacy, Anumita Roychowdhury, cautioned that the city is caught in a “deadly dilemma” as humid monsoon nights prove just as punishing as daytime heatwaves, forcing widespread use of cooling devices and straining the grid. “Our study shows how an increase in peak electricity demand is now happening earlier and persisting longer. But Delhi’s deadly dilemma is not only the high heat during the pre-monsoon months, but also the high humidity during monsoon months causing sharp increase in heat index (combination of heat and humidity). This is when the heat index goes beyond the threshold of thermal comfort to surge sharply as cooling devices are switched on across the city. This leads to sharper rise in electricity consumption, which strains grid reliability. Delhi has hit the second highest peak demand for electricity after 2024 summer,” she said.

The analysis found that during the monsoon period, Delhi’s daytime and nighttime land surface temperatures soared by about 2.1°C and 3°C respectively compared to 2024. The gap between these temperatures also narrowed, reducing the city’s ability to cool off at night and prolonging heat exposure for residents.

Power demand data underscored the sharp escalation. Peak demand rose by 567 MW, a 10.4% increase, from March to April 2025. Total energy consumption climbed from roughly 2,200 to 2,300 MW in March to more than 4,500 MW by June. In August, demand climbed further, with the all-time peak of 7,050 MW recorded on August 8. Despite monsoon cloud cover, Delhi still registered its second-highest peak ever, nudging past 8,400 MW and just below the 2024 record of 8,656 MW.

The report highlighted structural vulnerabilities worsening the crisis: warmer nights, heat-trapping concrete, dwindling urban greens and water bodies, and inadequate building design, all of which magnify stress on the city’s power system and public health.

In terms of remedies, the analysis recommended integrating heat index data into power planning, enforcing energy codes in new constructions, particularly affordable housing, and introducing mitigation measures such as cooling shelters, urban greening and enhanced grid resilience to counter the mounting risks.