Heat Index

  • The India Meteorological Department (IMD) is planning to introduce a ‘heat index’ warning system in Delhi and other parts of the country.


  • According to “Hot Weather Analysis over India,” IMD revealed that the mechanism by which heat impacts humans is complex; it is a result of the interactions between temperature, radiation, wind, and humidity.
  • There is strong experimental evidence that physiologic stress from high temperatures is greater if humidity is higher.

About the Proposed Heat Index

  • Heat Index will calculate the temperature along with the humidity levels to provide a more accurate measure of what the temperature actually feels like.
  • In the US, the heat index is color-coded to provide warnings based on the impact of the heat index.
    • The IMD is planning to introduce a similar color-coded warning system in India.
  • It will factor a day’s- Relative humidity, Wind speed, Maximum temperature, Cloud cover.
  • There is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (or decrease), the heat index increases (or decreases).
  • Usage of HI
    • It will not only warn against Heat waves hazard but also list precautions people can take.
    • Calculation of HI will help states in formulating better Heat Action Plans (HAPs) for heatwave assessment, forecast, preparedness and mitigation.
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