Lack of night cooling period poses risk to health: Experts

Thursday’s 31.9°C minimum — Delhi’s warmest May night in 14 years — brought with it a public health threat that operates outside the framework of heat advisories that typically focus on daytime exposure dangers.

- Ridhima Gupta and Jasjeev Gandhiok

scores of dead fish, attributed to heat by experts, at the Sanjay Van Lake on Thursday.

(RAJ K RAJ/HT)

Warm nights, doctors warn, deny the body its only recovery window, and for vulnerable populations without air-conditioners or coolers, the danger that accumulates after dark can be as serious as anything the afternoon sun delivers.

The mechanism begins with the buildings people sleep in. A study released last week by the research organisation Climate Trends, conducted across 50 low and middle-income households in Chennai between October 2025 and April 2026 using high-resolution sensor data, found that indoor spaces reached their peak temperatures not at midday but between 8pm and 9pm — as reinforced concrete structures released the heat stored through the day and remained above 34°C well into the night.