How Hot Is Too Hot?

Summary

Extreme heat is an increasingly regular feature of India’s climate, catalysing governments, public health agencies, and civil society to develop heat action plans (HAPs), policies, and emergency response measures to safeguard the public. Yet key questions remain unanswered about the thresholds that define dangerous heat and the evidence supporting interventions to mitigate its health impacts.

A central challenge in crafting any action plan or emergency response is deciding on its trigger point—the conditions above which exposure becomes hazardous and protective measures must be enacted. The most intuitive answer to the question “how hot is too hot?” is when conditions exceed the capabilities of human physiology. But this question cannot be answered without first asking, “too hot for what?” and also, “too hot for whom?” Even from a physiological perspective, these are difficult questions—and they become even more complex when translated into explicit triggers for HAPs, emergency responses, and other interventions.

A key barrier to deciding which interventions should be prioritised is a lack of data on their effectiveness, particularly in the Indian context. Even the establishment of robust evidence supporting the efficacy of an intervention does not guarantee that lives will be saved in the real world, as effectiveness can be compromised if the intervention comes with large economic costs. Identification and evaluation of solutions must therefore be heavily grounded in local context, to ensure feasibility and scalability in the long term.

This essay is part of the white paper, ‘Critical Perspectives on Extreme Heat in India’ by the Salata Institute’s Climate Adaptation in South Asia research cluster.