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July 07, 2010

Tom Spears is skeptical about the whole "feels like 44" humidex thing

As the temperature in Ottawa is set to rise about 30 again today, here's an interesting note about humidex from Ottawa Citizen science writer Tom Spears:
That brings me to the humidex. Don't believe it. When they say it's 33 degrees but "feels like 44," they mean there's moisture in the air. Hey, this is Ottawa. There's always moisture. We're in a river valley. Maybe 33 here compares to 44 with no moisture, but where do you find air with no moisture -- the Sahara? It does not compare to any experience here, and is a non-scientific judgment call that true meteorologists roll their eyes at, used only by TV and radio types to sound important. Yes, it's hot. It's 33 degrees, and you know what? This is what 33 feels like, without the need to inflate it. Read more from his blog...
Related: Ottawa Weather Guide


  1. I live in South Korea where the temperature from mid-June to Mid-September is always 30-38c with humiditiy around 90% - there is no humidex in the weather reports. Just temperature and humidity and warnings about keeping hydrated.

  2. I don't entirely agree with this, I've definitely felt a day of 33 with low humidity and a day of 33 with high humidity, both with and without sun- There has been a major difference. I think they key the term "Humidex" or "Humidity factor" to give people an understanding that the humidity has a play in how you'll feel and how much more quickly you'll become dehydrated. I've also felt it at close to 40 in other places with no humidex, it's a very different heat. So though it may not be exact or scientific, there is some truth behind it the fact that the humidity (and some will argue the dewpoint is more accurate to follow) levels DO make a great impact on how a person will feel from day to day.

  3. environment canada meteorologists do in fact use the humidex on the Meteorological Service of Canada (MSC) website. similarly to the windchill factor, the humidex is an approximation to what the day will feel like. and by the way, Tom, we don't have high humidity because of the river valley (that only contributes a small part to the humidity in the air), we owe it to the synoptic movement of larger masses of air coming up from the gulf of mexico. Even the Sahara desert air has moisture, more than you would guess. I would suggest getting your facts straight then make your opinion heard. I usually enjoy your pieces but this was a little ignorant.

