What is Wind Chill? Tips for Staying Warm

The wind can turn a mild winter day into a dangerous situation. Let’s talk about wind chill, the dangers associated with it, and tips for staying warm in cold weather.

The wind can turn a mild winter day into a dangerously cold day.

What is Wind Chill?

You might be surprised to learn that the wind chill factor was developed specifically to measure the risk of frostbite on cold days.

Air temperature alone can be misleading for predicting the risk of frost bite. This is because air temperature does not account for loss of heat due to convection.

On a cold winter day your body temperature warms the surrounding air creating, what scientists call, a “boundary layer.” This boundary layer acts as a protective heat buffer between you and the cold outside temperature. On a windy day, the body will lose heat more quickly as passing air removes this insulating layer.

You’ve experienced this type of cooling if you’ve ever used a fan on a hot summer day. While the temperature of the room remains the same, the fan helps push warm air away from the body.

In Canada, wind chill is calculated using a mathematical formula which takes into account the air temperature and wind speed. It can give us a better sense of what it feels like to be outside.

Wind Chill Dangers

Environment Canada has created a wind chill chart to help demonstrate the risks associated with prolonged exposure to cold weather:

Environment Canada's Wind Chill Chart shows how wind speed and air temperature produce wind chill temperatures. The chart shows the danger zones of frost bite. This chart describes the risk of frostbite given the wind chill temperature.

Notice that the outdoor temperature might be -15°C but with wind speeds of 45 km/h the temperature will feel like -28°C! This puts us at increased risk of frostbite.

Issues with Wind Chill

While wind chill can be helpful, it can also be misleading. Canadian meteorologist Brad Vrolijk has written an excellent post about its limitations here.

Some of the problems are in the way it is calculated. For example, wind chill assumes that all people lose heat at the same rate and that you are walking straight into the wind. It does not account for humidity, sunshine, clothing, and the type of environment you are in (sheltered by trees or in an open field). All these conditions will also affect how cold we feel outside.

Staying Warm While Hiking and Camping

Regardless of its limitations, the takeaway for those of us who spend a lot of time outside is that the wind can greatly increase how cold it feels. It can also increase our risk of cold related injuries like frostbite and hypothermia.

It’s always best to err on the side of caution. There are steps you can take to protect yourself from cold weather:

First, check the weather forecast. If the forecast is bad consider rescheduling your plans or cutting them short. Some GPS systems now come equipped with weather forecast apps which can help you assess the risks when you are backcountry.

Second, if you do plan on going outside in the cold ensure that you have the proper equipment to do so. You can minimize the risks by covering all exposed skin. I’ve written a post describing how to dress for cold weather.

Third, the cold can impair your ability to use your hands. Take this into account if you need to sett up camp.

Fourth, keep dry in cold weather. Any moisture on your body will cool you down.

 

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