UTCI max

 

Heat stress is not uniform across cities. Geographical, climatological and local factors shape how heat is experienced, making it essential to look beyond peak temperatures and examine exposure over time.

During April and May 2024, Delhi endured 98 hours of extreme heat stress, while Chennai faced 34 hours of the same. Yet Chennai experienced moderate or worse heat stress for 1,464 hours across the period, compared to Delhi's 926 hours. The difference lies in each city's character. Delhi, an inland city, sees intense daytime heat but benefits from greater diurnal fluctuation that brings nighttime relief. Chennai, as a coastal city, is moderated by the sea, which limits extreme spikes but sustains persistent humidity, keeping heat stress elevated throughout the day and night.

Different cities carry different heat signatures. Effective intervention requires a holistic reading of heat indicators, accounting for intensity, duration and timing in equal measure.