Question submitted by Phyllis Gee
(Burnaby, BC)
The humidex is an index (a computed value as opposed to something measured) devised to describe how hot or humid weather feels to the average person. The humidex combines the temperature and humidity into one number to reflect the perceived temperature. It takes into account these two important factors that affect summer comfort. It is therefore a better measure of how stifling the air feels than either temperature or humidity alone. A humidex of 40 with, for example, a temperature of 30 degrees means that the sensation of heat when it is 30 degrees and the air is humid is more or less the same as when it is 40 degrees and the air is dry. We must be careful not to depend on this interpretation alone: it is a mere indication of physiological reactions, not an absolute measure.
The humidex is particularly significant when its value is greater than 30. We only display humidex values of 25 or higher for a location which reports a dew point temperature above zero (0°C) and an air temperature of 20°C or more. Below this value, the humidex is too close to the air temperature to be considered significant.
Claire Martin is an award winning Senior Meteorologist for CBC News: Vancouver. She has over 20 years of experience ranging from official weather observing to operational forecasting to television broadcasting. She has worked for Environment Canada and the UK Meteorological Office in England. In 2005, Claire was awarded "Certified Broadcast Meteorologist" by the American Meteorological Society. The International Weather Festival awarded Claire Martin the honour of "Best Weather Presenter in the World" in 2000, 2001 and 2003.
