The humidex (short for "humidity index") is an index number used by Canadian meteorologists to describe how hot the weather feels to the average person, by combining the effect of heat and humidity. The humidex is a unit-less number based on the dew point, but it is equivalent to dry temperature in degrees Celsius. For example, if the temperature is 30 °C (86 °F), and the calculated humidex is 40, then it indicates the humid heat feels approximately like a dry temperature of 40 °C (104 °F).
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. Humidex differs from the heat index used in the United States in being derived from the dew point rather than the relative humidity.
The record humidex in Canada occurred on July 25, 2007, when Carman, Manitoba hit 53.0. This breaks the previous record of 52.1 set in 1953 in Windsor, Ontario.
The humidex computation formula 
When the temperature is 30 °C (86 °F) and the dew point is 15 °C (59 °F), the humidex is 34 (note that humidex is a dimensionless number, but that the number indicates an approximate temperature in °C). If the temperature remains 30 °C and the dew point rises to 25 °C (77 °F), the humidex rises to 42. The humidex is higher than the U.S. heat index at equal temperature and relative humidity.
The humidex formula is as follows:
See also 
External links 
Thu, 23 May 2013 04:53:36 -0700
Each and every workday, regardless of rain, snow or humidex, I walk to work. I've been doing it since I got my first post-undergrad job, although thinking back on my formidable years, I've been walking work as far back as I can remember. For me, it's a ...
Windsor Star (blog)
Tue, 21 May 2013 16:30:34 -0700
It was the fetid stench of garbage strewn everywhere, cooking under a soaring humidex. Paper plates, plastic cutlery, napkins, pizza boxes, empty bottles, a used grill — the detritus was spilling out of overflowing garbage cans all around the picnic ...
Mon, 13 May 2013 15:17:46 -0700
... Windsor typically has summers that are the third hottest in all of Canada, is ranked fifth in terms of receiving the most hot days (over 30 degrees Celsius or above), has the most thunderstorm days, smoke and haze days growing degree-days, humidex ...
Sat, 04 May 2013 04:02:26 -0700
I said it was probably for the best, then told him that I had to head'r. Hoser said “Later, Skookum,” and I hit the concession road heading west to Edmonchuck, where the humidex said it was plus 20, and so I ditched my hoodie, touque and bunny hug.
Tue, 07 May 2013 04:37:05 -0700
«On suit les directives de santé publique et on mesure régulièrement l'humidex. On distribue de la limonade et beaucoup de liquide aux résidants.» Encore faut-il que les employés aient le temps de bien hydrater chacun des résidants. Or, Annette ...
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