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Heat Index (HI)

GS Paper 3

 Syllabus: Geography/Disaster management


Source: TOI

 Note: This is in continuation of yesterday’s article on Heat Waves


Context: India Meteorological Department (IMD) is planning to issue a heat hazard analysis for India, including Delhi.

  • IMD will soon issue a Heat Index (in addition to the day’s maximum and minimum temperatures)


What is Heat Index?

It will be a colour-based warning that will give an estimation of what temperature actually feels like.


It factors Day’s

  • Relative humidity
  • Wind speed
  • Maximum temperature
  • Cloud cover.


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.


What are heat waves?

Heat waves are prolonged periods of excessively hot weather that may be accompanied by high humidity, often leading to a range of negative impacts on human health and the environment.

  • The heat wave is considered if the maximum temperature of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions.


Difference between Hazard, Risk, Vulnerability and Disasters:

Term Definition Focus Nature Example
Hazards Natural or human-made events or conditions that can cause harm or damage to people, the environment, or property. Source of harm Inherent Earthquakes, floods, fires, chemical spills, terrorism
Risk The probability or likelihood that harm or damage will occur as a result of exposure to a hazard. Probability of harm Calculable The likelihood of a flood, earthquake, or fire occurring in a particular area
Vulnerability The characteristics and circumstances of people, communities, or systems that make them more or less susceptible to harm or damage from a hazard. Susceptibility to harm Modifiable Poverty, lack of access to resources or information, age, disability
Disasters Events or situations that result in significant harm or damage to people, communities, or systems, often involve a combination of hazards, risks, and vulnerabilities. Consequence of harm Unpredictable Hurricane Katrina, COVID-19 pandemic, 9/11 attacks