Delhi Records Hottest Night in 14 Years as Urban Heat Crisis Deepens

Delhi recorded its hottest night in 14 years on May 25, 2026, with the minimum temperature reaching 32.4°C, according to a new CSE report that links the trend to urbanisation, loss of green and blue spaces and increasing air-conditioner use. The report, Making Delhi Heat-Resilient, calls for cool roofs, climate-sensitive urban planning and public cooling centres to manage escalating heat stress.

The CSE report documents a pattern of rapidly warming nights in Delhi, where post-sunset temperature relief has narrowed as the city's thermal mass — built up through concrete surfaces, dense construction and reduced vegetation — retains daytime heat well into the night. The May 25, 2026 reading of 32.4°C came in a period when daytime temperatures had already been above 40°C for much of the month, creating an extended heat stress window that increases risks of heat stroke, cardiovascular events and disrupted sleep, particularly among outdoor workers and households without cooling.

Night-time heat has disproportionate health consequences because the body relies on nocturnal temperature drops for physiological recovery from daytime heat exposure. The WHO links sustained high night-time temperatures to increased mortality, particularly among the elderly, infants and low-income populations with limited access to mechanical cooling. Delhi's pattern mirrors trends in cities globally, but the combination of extreme heat, dense poor-quality housing, and unreliable power supply makes the city's situation particularly acute.

CSE's policy recommendations include mandatory cool roof standards for new construction and retrofitting programmes for low-income neighbourhoods, expansion of shaded public cooling centres accessible to outdoor workers and the urban poor, and restoration of urban water bodies and tree cover as natural heat sinks. The report also urges revision of Delhi's heat action plan to include nighttime heat indicators in addition to daytime peaks. These measures have precedents in cities like Ahmedabad, whose heat action plan has demonstrably reduced heat mortality.

Key figure — 32.4°C minimum temperature on May 25, 2026 — hottest night in 14 years