Heatwaves and its effects on India 

  • Prelims: Climate Change, Air mass.
  • Mains (GS3): Conservation, environmental Pollution, Climate Change


A heatwave is a period of unusually hot weather with above-normal temperatures that typically lasts for 3 or more days. A heat wave is a situation of high air temperature that, when experienced by a person, is fatal. The period of heatwave in India is mainly during March to June and in some rare cases even in July. The peak month of the heat wave over India is May. It is the third biggest natural killer in India, with 2,040 people dying of them in 2015.

The prescription given by IMD suggests that a heatwave is considered if the maximum temperature at a station reaches at least 40 degrees Celsius for plains, at least 37 degrees Celsius for coastal stations, and at least 30 degrees Celsius for hilly areas.

Credit : Gyan Shahane


If normal maximum temperature is  ≤40 degrees Celsius, then an increase of 5 degree Celsius to 6 degree Celsius from normal temperature, is considered to be heat wave. An increase of 7 degree Celsius or more is severe heat wave condition.If normal maximum temperature of a station is > 40 degree Celsius, then an increase of 4 degree Celsius to 5 degree Celsius from normal temperature, is considered to be heat wave. More than 6 degree Celsius is considered to be severe heat wave.

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On lives and livelihoods:
  • According to a World Bank report, "Climate Investment Opportunities in India's Cooling Sector," from 2030, about 16 to 20 crore people would be exposed to lethal heatwaves in India every year, resulting in 3.4 crore people losing their jobs because of heat stress-related productivity decline.
  • Mortality because of the high temperature. According to a 2019 report by the Tata Centre for Development and the University of Chicago, more than 1.5 million people will likely die each year by 2010.
On food insecurity:
  • Heatwaves cause crop production losses and tree mortality to increase. An increase in heat waves can cause an increase in forest fires and a decrease in forest products.