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Cold Weather Considerations. Snow blindness (photokeratitis)


(Note: This Part 1 of a six-part series.)

If you live in the northern hemisphere then it’s that time of the year when things are getting cold and, depending on how far north you live, covered in white stuff. Around Thanksgiving I start planning my various winter outdoor activities such as hiking, camping, skiing and snowshoeing trips, and I thought it would be a good time to review some considerations for surviving and operating in winter conditions. Why would anyone want to be outside in the cold and snow? Because in a post-disaster scenario you may not have a choice, and being able to operate effectively outdoors in a winter environment can potentially provide you with a significant advantage since most people will probably be doing everything they can to avoid it. I know that a lot of you hunt in late fall/winter time, so I encourage you to share any tips or experiences you may have in the comments.

I link to a number of different products in this article – a lot of these are things that I own, have used, or have had significant interactions with people that have used them. I find they work well for me and my requirements, but you should do some research and figure out what would work best for you. You should also note that as with any outdoor activity, being outside in cold and snowy conditions can result in bodily harm and injury, so make sure you’re prepared and properly equipped, let someone know where you’re going and when you’ll be back, and always have some way to call for help in case of an emergency. If you’re new to outdoor winter activities do some research, take some training or participate with someone that has experience.

Since this is a long article that’ll be broken up into several installments I want to provide an overview of what I’ll be covering:

  • Health
  • Medical Treatment
  • Clothing
  • Shelter
  • Sleeping
  • Fire
  • Food
  • Water
  • Movement
  • Firearms
  • Electronics
  • Operational Considerations
What is ‘Winter’?

The beginning of winter is usually considered to be the shortest day of the year, but I consider it to be any extended period of time where the temperature will consistently stay below 60°F. Why 60°F? – because you can be subject to hypothermia in wet or windy conditions below 60°F, so you need to be prepared to handle those colder environments. Real winter also tends to bring a lot of interesting and exciting weather conditions such as extreme cold, snow, blizzards, freezing rain, ice, ice fog, temperature inversions, whiteouts, low humidity and wind chill effects, any and all of which can have significant impacts on your body and your operational activities in the outdoors. Generally it’s a good idea to avoid going outside in conditions that can kill you, but in a post-disaster world you may be forced to in some circumstances so you need to be prepared. I know that doing things like camping and hiking in winter conditions might seem somewhat frivolous and a little crazy, but I’d rather learn what works and how to do things right while I have safe fallback options rather than when I’m forced to.

Winter and Your Body

Given that you are arguably your single most critical prep, you need to understand how winter can impact your body. Your body produces heat mainly through metabolic processes in your cells as it breaks down food and converts it into energy. Glucose (sugar) from food reacts with the oxygen you breathe to produce carbon dioxide, water, and energy. Some of this energy is stored to be used later, and some of it is released as heat. This is referred to as cellular respiration and it is the main way your body generates heat.

Under normal conditions your body regulates the amount of heat produced to keep a stable core body temperature of around 98.6°F. While pretty much any cell in your body can produce heat, some muscles and organs produce more heat during certain activities, so your body moves heat around to where it’s needed using your blood. Hence, two of the most important considerations for staying warm are ensuring your body has enough fuel to produce heat, and the ability to move it around via your blood.

We’ll talk about food later on, but the movement of blood to warm you up brings up the first important consideration – chemicals like caffeine, nicotine and alcohol (in larger quantities) are vasoconstrictors, which mean they cause the capillaries that move your blood around to contract, reducing the flow of blood. The effect can last up to several hours, so this means that you should avoid things like coffee (except for decaffeinated), cigarettes, chewing tobacco, nicotine gum, vaping and beer when you’re going to be outside in the cold. I realize that’s probably a deal-killer for many of you, but I’ve found that a cup of hot chocolate with breakfast on a cold morning works just as well for me as a cup of coffee.

Your body also has an internal thermostat called the hypothalamus, which forces a series of actions when it gets cold, and one of the first things it does is make you start shivering. The goal is to increase your level of physical activity, thereby burning more calories and generating more heat. You may also start getting goosebumps – these are to make the hair on your skin stand up and help create a deeper boundary layer of warm air next to your skin. If you’re still cold after that your body begins to reduce the flow of warm blood to your outer layers in an effort to keep your insides warm. Next your breathing will slow down and you’ll probably start breathing through your nose, since that reduces the amount of heat lost during respiration. Eventually your hypothalamus will put you to sleep in a form of hibernation.

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The second facet of staying warm is knowing how heat is transferred into and out of your body. There are five possible mechanisms to consider:

  • Conduction – Conduction occurs when two objects at different temperatures are in physical contact with each other and the heat is transferred directly from the warmer object to the colder one. For example, if you’re warm and you lay down directly on the cold ground, your body heat will transfer into the ground; another example is your feet touching the soles of your boots, and you boots touching the ground. This is the most efficient form of heat transfer and will extract heat from your body faster than anything else.
  • Convection – Convection occurs when warmer areas of a gas transfer heat to cooler areas; this is a very poor method of transferring heat, which is why so many types of winter clothing rely on trapped air pockets for insulation. Your body also creates a warm layer of air next to your skin, which helps you stay warm, but the heat in this layer is constantly being transferred to the colder air around it, requiring your body to generate more. When the wind blows against exposed skin it rapidly removes this warm layer and you get wind chill.
  • Radiation – This is when heat is exchanged through the transfer of transmitted energy. For example, you feel warm when the sun shines on you due to the energy in the light from the sun being transferred to your skin and clothing. Warming your hands by a fire is also a form or radiant heat transfer. This is the least efficient method of transferring heat.
  • Evaporation – This is based on the fact that a liquid must have heat applied to it to change to a gas. When evaporation occurs, this heat is taken from the liquid that remains in the liquid state, resulting in a cooler liquid. Your body produces sweat to help you cool down through evaporation, and sweat evaporating in cold air can quickly chill you.
  • Respiration – Every time you breathe in, the air coming into your body is warmed up as it moves down through your larynx and trachea and into your lungs. Every time you breathe out that heat is being expelled out into the air.

One thing you need to be aware of is the myth that you lose more of your body heat through your head that any other part of your body; this was based on a seriously flawed study the British Army did back in the 1940s and has been proven to be false – any exposed skin will lose heat at roughly the same rate. That being said, your head and face are usually the most exposed parts of your body, so you need to make sure you insulate them appropriately.

Outside of freezing to death there are a number of other ways your body can be impacted in the winter:

  • Snow blindness (photokeratitis) is a painful eye condition caused by too much exposure to the sun’s UV rays and can cause permanent blindness. The most common symptom is a feeling of sand or grit in the eyes, but other symptoms can include watery eyes, bloodshot eyes, hazy vision, halos around lights, uncontrollable eyelid twitching, headache and eye pain, and your eyes may swell shut in extreme cases. Snow blindness may cause a temporary loss of vision or even permanent vision loss in extreme cases of repeated exposure. It’s a significant issue when the sun is out and reflecting off of large areas of snow or ice, which can reflect up to 80% of the sun’s UV rays. You need to make sure you have sunglasses or goggle that can protect you from the sun’s UV light, or search the web for articles on how make emergency snow goggles.
  • Excessive sun exposure (both direct and reflected from snow/ice) which can lead to sunburn. When you get sunburned your blood vessels dilate in an effort to increase the amount of healthy blood being brought to the area of the burn to aid in the healing process, which means you’re taking warm blood away from other parts of your body. If you suffer a particularly bad burn, your skin may develop fluid-filled blisters, which is absolutely no fun in extremely cold weather. Always carry some sunblock and chapstick, or completely cover up when you’re going to be out in the sun for any length of time in the winter.
  • Low humidity in the winter can cause dry, cracked or split skin, which can be extremely painful and could get infected. My biggest problem area is my fingers splitting around my nails, so I carry a tub of O’Keefes Working Hands. Low humidity can also significantly increase the amount of static electricity you generate, which can damage delicate electronics (and can be used to see how high a sleeping cat can jump 8-)).
  • Frostbite, which means that parts of your body have actually frozen, starting at your skin and working inward. Remember my earlier comments about caffeine/nicotine/alcohol reducing your blood circulation? The reduction in circulating warm blood to your extremities can be a significant factor in causing frostbite. The most common areas for frostbite are fingers and toes, since they’re farthest from your heart, followed by the nose and cheeks, since they tend to be exposed. There are four degrees of frostbite:
    • First Degree – Superficial surface skin damage that is usually not permanent. Early symptoms include the skin turning numb and possibly swollen, with a reddened border.
    • Second Degree – The skin develops clear blisters and the surface hardens. Later on the hardened, blistered skin dries, blackens, and peels.
    • Third Degree – The layers of tissue below the skin freeze. Symptoms include blood blisters and blue-grey discoloration of the skin. Later on pain persists and a blackened crust develops.
    • Fourth Degree – Structures below the skin such as muscles, tendon, and bone freeze. Symptoms include a colorless appearance of the skin, a hard texture, and painless rewarming. Later on the parts that froze may fall off on their own.
  • Dehydration is another common problem in the winter. Your sweat evaporates quickly, and for some reason this tends to short-circuit a lot of people’s thirst reflex, even if you’re losing as much if not more liquid than you may in the summer.
  • Slippery conditions significantly increase the odds of falls, which can result in bruises, sprains, muscle pulls and broken bones.
  • Chilblains (Perino) are a painful inflammation of small blood vessels in your skin that occur in response to repeated exposure to cold but not freezing air. Chilblains can cause itching, red patches, swelling and blistering on your hands and feet.
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Medical Treatment

We’ve covered several things in winter that can cause problems for your body such as hypothermia and frostbite, but it would obviously be useful to understand the symptoms and how these conditions should be treated. Starting with hypothermia, the symptoms include:

  • Confusion, memory loss, or slurred speech
  • Drop in body temperature below 95°F
  • Exhaustion or drowsiness
  • Loss of consciousness
  • Numb hands or feet
  • Shallow breathing
  • Shivering
  • A slow, weak pulse

Any one of those symptoms by themselves may not be an issue, but if two or more present then you should take immediate steps to treat that person. The most obvious (and really the only) thing to do is to warm the person up. You should focus on warming up the core, not the extremities, and avoid rapid changes in temperature like putting the person in hot water. If they have wet clothes get them in some dry ones, wrap them up in blankets or a sleeping bag and start a fire. If you have heating pads or hand warmers, put them inside with the person, but wrap them in some cloth to avoid direct contact with their skin. If you have warm drinks or soup you can give that to them, but avoid anything with caffeine or alcohol.

Frostbite treatment is similar – you need to gently warm the affected area back up. Note that until you can fix the problem that caused the frostbite in the first place you should avoid warming it up, as thawing and re-freezing will actually cause more problems. If the frostbite is on the toes or feet the person should avoid walking if at all possible. Use warm wet heat if possible – avoid direct contact with anything that’s hot, and don’t rub the skin. Cupping the exposed area with your hands and blowing on it to warm it up can also help.

Treating bleeding wounds in cold weather presents some unique challenges. If you need to cut clothing away to treat the wound and you’ll be outside for a while you’ll need to make sure you have some way of repairing or replacing the clothing so the person doesn’t get hypothermia or frostbite. The same applies for irrigating a wound – you need to try to avoid soaking their clothing with water. Having clean (unfrozen) water to irrigate can also be an issue (more details on water later) ; I always carry a sealed 8oz squeeze bottle of clean water and a small clean towel in a ziplock bag in one of my inside pockets to keep it warm, but you could also carry single-use bottles of saline.

Lastly, we discussed how cold can cause vasoconstriction which reduces blood flow, which can slow down healing. Keeping a wounded person warm is critical to prevent shock and promote healing.

(To be continued tomorrow, in Part 2.)



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