The India Meteorological Department (IMD) declared 2024’s first heatwave conditions for isolated pockets of west Rajasthan on March 27, 2024.
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.
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.