How is Wind Chill Determined?
You check the weather and forecast regularly. Knowing what the weather is like and what it possibly might be like is not only an essential part of wilderness exploration, hiking, camping, mountaineering—but critical during tactical situations or simulations. There's no way to predict exactly what will happen when you're far from the road and cell service is nonexistent. So knowing what you're going to and might encounter can literally be life-saving, as you can pack and supply accordingly.
What does it mean when the weather app you use or the weatherman says the temperature is -11 but it 'feels like -20?' If you're new to weather tracking for your upcoming outdoor adventures, you might begin wondering how that 'feels like,' is determined. Is there some sort of special thermometer out there?
We explain how wind chill is determined, what it is, and why it's so important to consider wherever you're going and whatever you'll be doing out in the winter wind chill.
What is wind chill? Why does it make us feel colder?
Whenever the wind blows across an exposed surface, such as our skin, it draws the heat away from our bodies. Air trapped between our skin and our clothing, such as base layers, wool, and outer shell keeps us warm by trapping air that our body heats. High winds in poorly insulated clothing, or without the right type and material layers, will simply blow the trapped air before it can be heated.
The faster the wind, the more heat that is drawn away from you and the more your skin is exposed to the constant wind, the lower your body temp drops, and quicker than it would on a still winter day.
When we see, "feels like," temperature, this is a measurement of how truly cold—or in summer's case—hot it really feels outside with the addition of environmental data such as wind gusts or humidity which in summer make it feel hotter than usual. Data that includes the ambient air temperature, humidity and wind speeds are calculated together to determine how weather conditions really feel to bare skin.
Who was it that came up with the idea for measuring wind chill?
The idea of measuring wind chill is credited to an American explorer and geographer, Paul Siple and his fellow explorer, Charles Passel. They made their first breakthrough in wind chill research while on an expedition in the Antarctic during the 1940s. They suspended bottles of water outside a hut at the base station they were currently at and began measuring how long it took the water to freeze under various wind conditions.
They took hundreds of temperature readings and after comparison, the two of them began forming the idea of how rapidly heat was lost at differing wind speeds.
What is wind chill exactly?
When the two explorers were conducting their research, they weren't trying to develop a temperature equivalent. Their original measurements expressed heat loss in a simpler unit: watts per square meter.
It wasn't until the 1970s that the language use of, "feels like," began being used on the news. Before the switch, weathermen would report the wind chill in three or four-digit numbers which were a bit difficult for viewers at the time to wrap their heads around. American weathermen started translating wind chills into temperature equivalents in order to give viewers at the time a more familiar term to understand.
Surfaces, including our skin, lose heat through conduction, evaporation, convection, and radiation. Wind chill removes the insulating boundary layer of warm air that naturally forms against your skin and between layers you wear in the cold. And the faster that wind is, the higher the wind chill and more rapidly your body cools.
What's the formula used for factoring wind chill?
Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)
If you've ever wanted to figure it out on your own with a trusty calculator, thermometer, and anemometer because you do not have access to the weather channel, wi-fi, weather app, and other similar weather forecasting tools, the above is the Fahrenheit version of the equation that calculates wind chill factor.
T represents the air temps in degrees Fahrenheit, V is equal to the wind speed in miles per hour.
What is the point again, of noting the wind chill factor?
The basic concept behind wind chill is that the stronger the wind, the faster any exposed or poorly insulated skin begins to cool. The faster the skin cools means the quicker frostbite can set in, which is a serious medical hazard for outdoor activities in colder climates and winter. It is essential for safety, preparedness, and should always be a deciding factor into what you'll be putting in your backpack, and what sort of protection, food, and gear you'll need.
Surviving in harsh weather and being prepared for the worst means never being caught off guard. We encourage you to always make sure you factor in the wind chill no matter the cold or winter activity.