“Humidex is like wind chill; meteorologists make it up to scare us!”
That’s a real quote taken from a post on my Facebook page.
I’ll start by saying that humidex is real, it’s Canadian and it’s important.
A humidex is a number used by Canadian meteorologists to reflect the combined effect of heat and humidity. The humidex, often called the “feel-like” temperature, is not an actual temperature. It’s not measured; it’s calculated, so it’s a value.
Many people struggle with the concept of humidex. The problem is, there is no objective way to put a number on what something “feels like” or how someone feels, therefore an arbitrary base had to be chosen. So, the humidex is a measure of what temperature it would feel like based on a dew point of 7 C. 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.
According to the experts, a humidex of 30 or more causes “some discomfort,” 40 causes “great discomfort” and above 45 is “dangerous.”
The record humidex in Canada occurred on July 25, 2007, when the calculated feel-like temperature reached 53 in Carman, Man. That broke the previous record of 52.1, set in 1953 in Windsor, Ont. The residents of Windsor would not have known this at the time since the humidex had yet to be invented.
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. He named it the “humiture.” It was renamed the heat index and adopted by the U.S.’s National Weather Service a year later.
When will it end? This round is almost over. A cold front will sweep down across the region triggering late-day showers and a wind shift to the northwest. Behind it, the sun returns… without the high humidity.
In the meantime, stay cool and hydrated and keep an eye on your pets!
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Cindy Day is the chief meteorologist for SaltWire Network.