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.

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.