It’s not the heat, it’s the humidity… at least that’s what they say! 

By 11 o’clock this morning, humidex values ranged from 25 to 32 across all three Maritime Provinces.

Last summer, during a particularly hot stretch of weather, someone stopped me on the street and said that by “inventing” the humidex, meteorologists are making it sound hotter than it really is.  That really is not the case; we’re simply trying to give people a better idea of how it “feels” outside.

The humidex is a number used by Canadian Meteorologists to reflect the combined effect of heat and humidity. According to the Meteorological Service of Canada, a humidex of at least 30 causes "some discomfort", at least 40 causes "great discomfort" and above 45 is "dangerous." When the humidex hits 54, heat stroke is imminent.

The current formula for determining the humidex was developed by J.M. Masterton and F.A. Richardson of Canada's Atmospheric Environment Service in 1979. The term is widely used in Canada during the summer months in weather reports.

To complicate matters, you might have heard the term Heat Index used during weather broadcasts south of the border. The heat index uses a dew point base of 14 °C.  The heat index was developed in 1978 by George Winterling as the "humiture" and was adopted by the USA's National Weather Service a year later.  

The record humidex in Canada occurred on July 25, 2007, when Carman, Manitoba hit 53.0.  This broke the previous record of 52.1 set in 1953 in Windsor, Ontario.  The residents of Windsor would not have known this at the time, since the humidex had yet to be invented.

Stay cool and hydrated…and keep an eye on your pets!

Chief Meteorologist

Cindy Day