The Wind Chill Phenomenon
- How does it apply to me? What does it mean?

The morning news reports that the temperature is -15°C (5°F) but that the Wind Chill Temperature Index is at -28°C (-18°F). The Mountain Organic Natural Icemelter you just bought is effective to -23°C (-9°F); is there any point in applying it? Will the icemelter work when the wind chill is below the effective melting point of the product?

Yes, you should apply the icemelter. Wind chill temperature has no effect on inanimate material, so you don’t need to be concerned about the wind chill temperature when it comes to applying icemelt, according to XYNYTH Manufacturing, a leading North American manufacturer of icemelters. For wind chill, it is your skin that is at issue.

Our bodies have a method of protecting us from cold. We naturally warm up a thin layer of air close to our skin which is known as the boundary layer, and when the wind blows this away, we lose our insulation. Additionally, wind takes heat away from the body by evaporating any moisture that is on your skin. You’ve probably had personal experience with this phenomenon – on a hot day, when you get out of the pool, you might feel cold as the breeze evaporates the droplets of water on your skin. Your driveway or parking lot is not affected by these features – except insofar that a windy day will help disperse the moisture that is created by the action of the icemelter you use.

The wind chill factor was first based on research in the 1940s that measured the cooling rate of a container of water hanging from a tall pole. The method was a bit primitive and didn’t take into account the fact that water will freeze faster than flesh. The original wind chill index therefore underestimated the time to freezing, and overestimated the cooling effect of the wind.

In 2001 new research was conducted that took advantage of advances in technology. The new Wind Chill Temperature Index was developed using human subjects walking on a treadmill in a wind tunnel. Facial temperature readings were recorded in order to gain accuracy in the new formula and to determine frostbite levels. The new index therefore has several advantages over the old one:

• Wind speed is calculated at five feet – the average height of an adult human face – rather than a tall pole
• Human faces were the basis for the data, not a container of water
• It incorporates modern heat transfer theory
• Calm wind threshold is calculated at 3 mph (the old index used 4 mph)
• A consistent standard for skin tissue resistance is used
• No impact from the sun is considered.

The new index is therefore much more accurate and useful than the one used up until 2001.

By expressing the outdoor conditions as an equivalent temperature without wind, the new Wind Chill Temperature Index conveys the amount of ‘chill’ your skin will sense. If the wind chill is -28°C (-18°F), but the air temperature is only -15°C (5°F), the index is denoting that your face will feel as cold as if it really were -28°C (-18°F) on a calm day.

A frostbite indicator is built into the new index as well. In the example above, it isn’t your parking lot you would need to worry about; a Wind Chill Temperature Index reading of -28°C (-18°F) puts any exposed skin in danger of frostbite within 30 minutes. See the chart below for a breakdown of frostbite danger levels

 

Source: Environment Canada.
Environment Canada provides seven steps to cold weather safety.

Seven Steps to Cold Weather Safety

• Listen to the weather forecast, or check a local weather website before going outside. Now that you know what the Wind Chill Temperature Index is telling you, make sure you consider how cold it will feel out there.
• Plan ahead. Think about shelters that you can step into if needed, and plan for warm-up breaks if you’re working outside.
• Dress warmly in layers, with a wind-resistant outer layer. Wear a hat since a large amount of body heat is lost through the head. Mittens are better than gloves, and use something to keep your face protected, such as a scarf or facemask. If the wind chill is significant, cover as much exposed skin as possible. Don’t forget waterproof, insulted footgear too.
• Seek shelter – the wind chill effect can be defeated if you get out of the wind. Limit your outdoor activities when the thermometer plummets.
• Stay dry as evaporating moisture will chill you very rapidly. If you are working outdoors and generating sweat, open your coat or remove a layer of clothing to reduce the moisture build-up.
• Keep active so your body heat will increase and keep you warm.
• Be aware. Watch out for signs of frostbite and keep an eye on children. Check on your elderly neighbours to make sure they’re coping, and remember that alcohol, tobacco, and some medications will increase your susceptibility to the cold.

If you need to be outside during this winter’s extremes, be careful and remember that wind chill is a real effect that can cause frostbite at temperatures lower than you might expect.

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