What is ‘Apparent Temperature’?

apparent temperature
What the heck is AT?

Pedram Fard and Chirag Patel


January 14, 2024


January 14, 2024

In a few of our posts, we talk a lot about apparent temperature. What is it and how is it calculated?

While different measures have been developed in epidemiological research to quantify heat and cold exposure, a composite is a solution for extreme heat and cold exposure assessment.

We used the apparent temperature (AT) as it allows for a holistic representation of thermal comfort and perceived temperature by incorporating factors such as relative humidity and wind speed in addition to the ambient temperature.

AT is derived through a linear combination of actual temperature, vapor pressure and wind speed in metric units and interpreted in Celsius (°C), where:

\(AT = −2.7 + 1.04T + 2.0P − 0.65u\)

AT: Apparent Temperature Index in °C
T: Temperature in °C
P: Vapor pressure in kPa
u: Wind speed in m/s