Perceived Temperature

▣ What Is “Perceived Temperature”?

Perceived temperature refers to the temperature that people actually feel, which takes into account not only the air temperature but also factors such as wind and humidity.

In other words, even if the air temperature is the same, stronger winds or higher humidity can make it feel colder or hotter. Perceived temperature expresses this difference as a measurable value.

In summer, it is typically determined by considering both air temperature and humidity. Humidity plays a key role because when it is high, sweat evaporates less efficiently, reducing the body’s ability to release heat—thereby increasing the risk of heat-related illnesses.

▣ Concept of Perceived Temperature

Actual temperature	The air temperature measured with a thermometer.
Perceived temperature	The temperature felt by the human body, taking into account the effects of wind and humidity

▣ Calculating Perceived Temperature

1) Summer perceived temperature – Calculated using air temperature and humidity (e.g., Heat Index)

2) Winter perceived temperature – Calculated using wind speed and air temperature (e.g., formulas used by Environment Canada)

▣ Perceived Temperature and Health

High perceived temperature – Increases the risk of heatstroke, dehydration, and cardiovascular problems.
Low perceived temperature – Increases the risk of frostbite and hypothermia..

▣ Heat Index

The heat index is a measurement used to estimate how hot it feels by combining air temperature and humidity.

▣ Factors Affecting Perceived Temperature

1) Summer: Humidity

When humidity is high, sweat evaporates less efficiently, making it feel hotter and more uncomfortable.
Example: At 33 °C with humidity above 80%, the perceived temperature can exceed 40 °C.

2) Winter: Wind

Wind increases heat loss from the skin, making it feel colder.
Example: Even if the air temperature is 0 °C, strong winds can make it feel like –10 °C or colder.