Winter weather can sap the warmth from your body in four ways:
- Radiative Heat Loss occurs when your body heat simply escapes into the cold air due to lack of insulation.
- Convective Heat Transfer happens when the wind draws heat away from your body, especially from exposed skin.
- Conductive Heat Transfer occurs through direct contact with cold surfaces or liquid, such as sitting on the snow, wearing a sweaty shirt under your jacket or falling into a frozen lake.
- Evaporative Cooling takes place when perspiration evaporates, drawing body heat with it.
Understanding Wind Chill
Although it may be 15 degrees outside, 15mph winds can make it feel more like zero. Wind chill is based on a combination of both air temperature and wind speed (i.e. radiative and convective heat loss). Check out the National Weather Service: Wind Chill Chart for more information on how wind increases exposure levels in cold weather.
Although you probably don’t have to worry about hypothermia during a walk to your mailbox, the danger of exposure can become a real threat if the weather takes a turn during a late-season hike, backcountry skiing trip, snowshoeing trek or winter camping venture. Being prepared with additional clothing and gear is the first step to winter safety, but recognizing the signs of exposure could also save your life, or the life of a friend or loved one.
Hypothermia occurs when a person's core body temperature drops too low, and it’s possible to get hypothermia at temperatures above freezing. When your body loses too much heat, common symptoms include excessive shivering, weakness or exhaustion, fumbling hands, confusion, memory loss and slurred speech. There are several phases of hypothermia, but continuous shivering is usually the first sign that you need to increase your protection from the cold or seek shelter. Prolonged hypothermia can be life-threatening. Below are four ways to raise your core temperature:
- Find shelter, especially from the wind, even if it’s just wrapping yourself in an emergency blanket or hunkering down beneath a tree.
- Remove any wet clothing and replace it with dry clothing, if possible.
- Focus on warming your core first, i.e. your torso, neck, head and groin. If another person is available, skin-to-skin contact under loose, dry layers of clothing or inside a sleeping bag can transfer vital warmth to a person suffering from hypothermia.
- Drink heated beverages, such as hot tea or soup. Avoid drinking alcohol, as this could actually lower your body temperature.
Frostbite occurs when your flesh actually begins to lose blood circulation and freeze. Extremities like fingers, toes, ears and noses are almost always affected first. Exposed areas also tend to be affected first, but frostbite can occur without direct exposure to the air. Even if you have a safe core body temperature, your extremities could still be at risk, especially in severe cold and high winds.
Numbness and tingling in your extremities is usually the first sign of frostbite, although you may not actually feel anything. If treated early enough, frostbite is reversible. Advanced warning signs include white or grayish-yellow skin at the affected areas. Frostbitten skin may feel unusually firm or "waxy.” If exposure continues, the flesh will essentially begin to die, leading to permanent damage, which may result in the need for amputation. Remember: You might be unaware of frostbite, because once you have it, the frozen tissues are already numb.
How to deal with frostbite (if medical care is unavailable):
- Seek shelter and warmth as soon as possible. Focus on warming your hands first by placing them in your armpits or between your thighs. Next use your hands to warm your toes, ears and nose.
- You may also immerse affected areas in warm water, but never use hot water.
- Do not continue walking on frostbitten feet or toes unless absolutely necessary, as this can increase tissue and nerve damage.
- Don’t massage the affected area too vigorously. Never use a hot object directly against the skin. Affected areas will be numb and you could easily burn yourself.
Bottom line: Exposed skin is more likely to get frostbitten. In very cold weather, cover all exposed skin. However, you can still get frostbite without actual skin exposure. If your toes have been numb for more than fifteen minutes, you could already have early stage frostbite.
You can avoid hypothermia, frostbite and discomfort simply by dressing properly for the conditions. But don't decide what to wear simply based on the forecast. In 32-degree weather, someone snowshoeing uphill will feel much warmer than someone sitting motionless in an unheated ice fishing hut. Decide which type of activity you'll be doing before you make a decision on how to dress. You should also always be prepared with extra clothing, just in case conditions become worse.
Activities like ice fishing or stand hunting require thick insulation around your core and between you and cold surfaces. Consider sitting on a foam pad to protect your body from conductive heat loss.
Activities like hiking, snowshoeing and cross-country skiing involve very little motionless time. For these sports, focus more on covering extremities and less on insulating your core. This will prevent overheating and excessive sweating. Also, be sure your base layer is breathable and moisture-wicking.
When there’s an even mix of exertion and motionless rest, layering becomes much more important. A good example is alpine skiing, which involves sitting on a cold chairlift in between runs. Outerwear with zip-open vents can help expel excess heat when you’re skiing, or you can simply shed a layer when you get off the lift. When you’re on the lift, you can close the vents, pull up your hood and bring out a scarf to protect your face.
Basic Layering for Winter
No matter what you're doing outside during the winter, layering will make adapting to changing conditions and activity levels much easier. Proper layering allows you to remove or add insulation so that you never get too cold or too hot. This prevents excessive sweating, which can cause additional heat loss, especially when you slow down or stop to rest. There are three main "under-shell" layers to consider:
• The base layer is worn directly against the skin. In winter, this layer often includes long underwear. The best base layers are made of polyester, polypropylene, merino wool, silk or other materials that wick moisture and dry quickly. In more moderate weather, this layer may simply include a lightweight T-shirt.
• The mid layer typically includes a long-sleeved shirt. Button-up shirts are a good choice, because they are easy to take off and put back on, as needed.
• The insulating layer acts as your primary source of warmth. Examples include a fleece pullover, fleece vest or wool sweater. In very cold weather, a down vest or jacket may be used as an insulating layer.
For more detailed information on layering, visit our Layering Guide.
Once you have your other layers, what you wear on the outside is the final piece of the puzzle. Your outerwear must do three things: block the wind, keep out rain and snow, and allow sweat vapor to escape. For drier conditions, a water-resistant jacket or soft shell jacket should be sufficient. If you could encounter very wet or snowy conditions, look for waterproof breathable protection from materials like Gore-Tex® or Dry.Q® by Mountain Hardwear. Soft shell outerwear, on the other hand, uses technologies like Schoeller® for added stretch and breathability, although usually with a slight reduction in waterproof protection. Check out our Waterproof Guide for more info on how we quantify what is and isn’t waterproof.
Depending on the conditions, your outerwear may include both a jacket and waterproof pants. One big consideration when shopping for outerwear is whether to choose an insulated jacket and pants, or go with uninsulated shells. Generally, only choose insulated outerwear for more sedentary activities or if you feel that you frequently need additional warmth. For more rigorous activities like skiing and snowshoeing, it's usually best to stick with an uninsulated jacket and pants. Proper layering will allow you to adapt your comfort level to changing conditions.
Once you know a little more about frostbite, it's easy to understand the importance of keeping your extremities covered and insulated from the cold. In this section we’ll cover the winter outerwear accessories you’ll need to stay well-protected.
Winter Hats & Beanies
In cold weather, you can lose a fair amount of warmth through your head, if left unprotected. Winter hats and beanies are available in a wide range of styles and materials. Synthetic fibers like Windstopper® polyester and acrylic wick moisture and dry quickly. Wool is another warm, wicking material for winter headwear. For moderate conditions and high activity levels, a fleece headband is a good alternative to a beanie.
Face & Neck Protection
For very cold and windy conditions, a face mask or balaclava can be a life saver, especially on the ski slopes and at high elevations. A scarf can also be used to provide neck and face protection.
Gloves & Mittens
Having a warm pair of winter gloves or mittens is critical to staying comfortable in cold conditions. In very cold weather, insulated mittens keep fingers warmer than gloves. Another option is to buy winter gloves and an additional pair of glove liners for extra insulation. Some ski gloves actually come with built-in, removable liners.
Cold-weather footwear can range from heavy-duty snow boots and pac boots to more basic insulated shoes and booties. Many winter boots have a “comfort rating,” such as “comfort-rated to -15 degrees Fahrenheit.” This will give you an idea of how much insulation a pair of boots will provide. Just be aware that there is no industry standard for footwear comfort ratings, and these numbers are estimates created by the manufacturer. Be sure to note whether the comfort rating is listed in Fahrenheit or Celsius, although some brands list both. Always wear warm, midweight or heavyweight winter socks with your snow boots. Check out our Winter Boot Guide for more information.
Other Winter Accessories
Winter conditions can actually amplify your exposure to UV rays, which are reflected off the surface of the snow. This makes a pair of goggles or sunglasses an important item to have for bright, sunny days on the ski slopes or out on the snowshoeing trail. Check out our Sunglasses Guide for more info on lenses and sizing. Hand warmers and foot warmers from brands like Grabber are another handy item to have with you when the temp drops. Pop a few in your jacket pocket, and you’ll be glad to have them if the wind chill picks up.
Having warm clothing and a few other items in your car during winter could potentially save your life if you ever slide off the road and become stuck in the middle of a bad snowstorm. This is particularly important if you plan on traveling through any rural or remote areas in winter. Depending on the road conditions and how far from town you are, rescue may not arrive for hours or longer, so it’s important to be prepared for the worst with a basic winter car survival kit. Consider carrying the following items:
- Sleeping bag and warm blanket
- Winter boots
- Extra pair of warm socks
- Insulated jacket or coat
- Gloves, scarf and winter hat
- Full water bottle
- 2-3 energy bars or other snacks
- Flashlight with extra batteries
- Road flares or emergency light
- Small snow shovel
- Cell phone and car charger