Heat Index

What is Heat Index ?

Generally, in weather reports, they give an actual temperature and then a “feels-like” temperature. This “feels-like” temperature is much higher than the actual temperature.

This “feels-like” temperature is known as Heat Index.
Heat Index is based on 2 variables
1. Actual Temperature
2. Humidity

To identify the heat index, the following standard table can be used. 
According to this table, when the actual temperature and the humidity are known, the heat index can be identified.

Figure 1: Standard Heat Index Table

Generally, when the heat index gets higher than 105, it is not good. So it is very essential to use not only the outdoor temperature but also the heat index when planning outdoor activities.


Annual Monthly Variation of Heat Index  2018/2019

Figure 2. These cycles are characterized by mean of monthly Heat Index values over the period 1986-2016.

 An upward shift in the HI values is noticeable throughout 2019.

Heat Index Ranges
80-90 = Caution
91-104 = Extreme Caution
105-129 = Danger
Greater than 130 = Extreme Danger



Monthly Average Heat Index 2019

Figure 3: Monthly Average Heat Index of Sri Lanka for the First 6 Months of 2019.
*For Sri Lanka, the color scale used for Heat Index mapping is different from the standard color scale of the Heat Index.


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