Indian summers are getting hotter, but is it the heat or is it us? Premium

India's intensifying heat waves demand urgent action to protect health, economy, and communities from escalating impacts.

Every summer, a familiar question surfaces across India, echoing from homes to newsrooms: is it genuinely hotter, or have we simply become more sensitive? This isn’t just some nostalgic lament or biological quirk. The evidence is clear and uncompromising: India’s heat is intensifying, creeping in earlier, stretching longer, and striking deeper than ever before.

What’s happening isn’t a trick of perception. It’s real. Heat waves, once occasional and brief, have become persistent forces reshaping daily life and work. According to the India Meteorological Department, a heat wave is declared when the temperature reaches at least 40° C in the plains or 30° C in the hills, with a deviation of 4.5° C or more above normal for at least two consecutive days.

These thresholds, once rare, are quickly becoming the standard during summer months. In states like Odisha and Rajasthan, what used to be brief seasonal heat spikes now stretch into longer, more frequent episodes, cumulatively spanning months. Between June 2010 and the summer of 2024, cumulative heat wave days soared from roughly 177 to 536 — a staggering increase of over 200%.

Heat wave days count the total number of days on which heat wave conditions are recorded across all affected regions. Since heat waves strike different places at different times, these days are summed nationally, so the total may surpass the length of the summer season in any single location.

Despite the increasing severity of heat waves, official data likely underrepresents their true impact. Various government departments collect and report heat-related deaths using different methods and sources, which can lead to variations in the numbers presented. Between 2000 and 2020, India recorded 20,615 heatstroke deaths, according to government records. However, many heat-related fatalities occur outside hospitals — at homes, construction sites or village farms, for example — where medical assistance and formal death certification may not always be accessible. As a result, deaths triggered by heat are often recorded under broader causes like cardiac arrest or respiratory failure.

The absence of standardised, mandatory heat-related death reporting and real-time surveillance means many such deaths remain uncounted, creating challenges for public health planning and response. Independent researchers and organisations have sought to address this gap using excess mortality analysis: comparing actual deaths during heatwave periods with long-term seasonal averages.

While some critics question the accuracy of these estimates and the methods used, excess mortality analysis remains a widely accepted and robust epidemiological tool. It captures both direct and indirect deaths related to heat, including those misclassified under other causes such as cardiac arrest or kidney failure, which are often missed in official counts.