# Heat Index - Important Facts for UPSC

Heat index gives the measure of humidity. This is also known as apparent temperature. The heat index is the temperature that is felt when the relative humidity is combined with the air temperature in shaded areas.

It is a key concept for theÂ IAS examÂ and can be better understood with the relevant details given about it in this article.

## Important Facts about Heat Index

 Heat IndexÂ Simple Definition of Heat Index An index that combines air temperature and relative humidity in shaded areas to put forward a human perceived equivalent temperature.Â What is Heat Index also called as? There are different terms given to Heat Index: Felt Air Temperature Apparent Temperature Real Feel The concept Head Index was developed in 1978 by George WinterlingÂ  US National Weather Service adopted it in 1979 Heat Index contains assumptions onÂ Human body mass and height Clothing Amount of physical activity Individual heat tolerance Sunlight and ultraviolet radiation exposure Wind speed

### How to Calculate Heat Index?

The heat index is calculated based on actual temperatures and relative humidity levels.

The heat index is calculated based on the result obtained from the heat index graph when relative humidity is compared against actual temperatures.

### When was the Heat index introduced in India?

Indiaâ€™s first-ever heat Index was introduced by the Indian Meteorological Department in 2016. The heat index provides the citizens accurate and updated information on the heat conditions specific to their areas.

In 2017, IMD brought an interactive map charting the heat index status in different states of the country.Â The interactive map denoted colours, varying from blue to orange, which indicates the stress placed on human beings by the climatic conditions of the time.

### What are the different alerts as per the Heat Index?

The different alerts as per the Heat index are mentioned below:

 Classification Heat Index Caution 80 degree F – 90 degree F High Alert 90 degree F – 103 degree F Danger 103 degree F – 124 degree F Extreme Danger 125 degree F or higher

In addition to the terminologies described above in the table, the index also comprises a colour coding to provide the range of alerts. The Heat index can also be used to retrieve information on health hazards if the temperatures and humidity levels cross a particular value.

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