Indians may already be experiencing temperatures close to limits of human survivability without even being aware
The India Meteorological Department (IMD) declared 2024’s first heatwave conditions for isolated pockets of west Rajasthan on March 27, 2024. But there are many more places that likely suffered from humid heatwaves and will continue to do so in the next few days. These are not being accounted for in IMD’s heatwave data.
The basic criteria for IMD to declare a heatwave is when the temperature of a place crosses 40 degrees Celsius (°C) in the plains, 37°C in the coastal areas and 30°C in the hills. These temperature values are the thresholds set by IMD for the declaration of heatwaves in India.
Apart from this, the temperature of a particular day has to be above normal by at least 4.5°C for two consecutive days for a heatwave to be declared.
When the temperature crosses 45°C, the weather agency immediately declares a heatwave without considering the deviation from normal temperature for that particular place. But this criteria does not take into account relative humidity, which is increasingly becoming a cause of humid heatwaves.
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