IMD May Revise Heatwave Criteria As Climate Change Intensifies Extreme Weather

The India Meteorological Department (IMD) is considering changes to the parameters used to declare heatwaves in the country, amid growing concerns that climate change is making extreme heat events more frequent, intense and prolonged.

Officials said the existing criteria, developed years ago, may no longer accurately reflect present-day weather realities as rising temperatures continue to alter seasonal patterns across India.

At present, IMD declares a heatwave based on maximum temperature thresholds and departures from normal temperatures in different regions. However, experts are now examining whether additional factors — including humidity, duration and night-time temperatures — should play a greater role in assessing heat stress.

The review

comes after several parts of India experienced severe heat episodes in recent years, with temperatures crossing 45°C in multiple states and heat-related illnesses increasing.

Scientists and weather experts have argued that heatwaves are no longer defined solely by high daytime temperatures. Rising humidity levels and persistently warm nights can prevent the human body from recovering, increasing health risks even when traditional heatwave criteria are not met.

Climate researchers say global warming is contributing to more dangerous heat events, making older benchmarks less effective in capturing the real impact on public health, agriculture and infrastructure.

The IMD’s move is also linked to broader international discussions on improving heat-risk assessment as countries adapt to climate change.

India has witnessed a rise in extreme weather events in recent years, including prolonged heatwaves, erratic rainfall and intense storms. Experts warn such events could become more common if global temperatures continue rising.

Any revision in IMD’s heatwave declaration standards could influence early warning systems, disaster preparedness measures and public health responses across the country.

Officials have indicated that discussions are ongoing and revised criteria, if approved, would aim to improve forecasting accuracy and better protect vulnerable populations from extreme heat.