Information on Apparent Temperature

Information on Apparent Temperature

Apparent Temperature is calculated with the wind speed, direction, humidity, and outdoor temperature on a fully clothed human body. Apparent Solar Temperature calculates all the above factors, but it also adds the Solar Intensity.

Apparent Temperature is a measure of relative discomfort due to combined heat and high humidity. It was developed by R.G. Steadman (1979) and is based on physiological studies of evaporative skin cooling for various combinations of ambient temperature and humidity. The Apparent Temperature equals the actual air temperature when the dew-point temperature is 14°C (57.2°F). At higher dew-points, the Apparent Temperature exceeds the Actual Temperature and measures the increased physiological heat stress and discomfort associated with higher than comfortable humidities.

When the dew-point is less than 14°C (57.2°F), on the other hand, the apparent temperature is less than the actual air temperature and measures the reduced stress and increased comfort associated with lower humidities and greater evaporative skin cooling.

Apparent temperatures greater than 26.6°C (80°F) are generally associated with some discomfort. Values approaching or exceeding 40.5°C (105°F) are considered life-threatening, with severe heat exhaustion or heatstroke possible if exposure is prolonged or physical activity high. The degree of heat stress may vary with age, health, and body characteristics.