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Safe, Warm, and Dry - The Mechanics of Winter Heat Loss and Retention

2026-01-26

<h3>Introduction:</h3>

I despise the cold.

During a conversation with my therapist in 2021, I confessed that the idea of getting up before the sun and running in freezing temperatures was the sole reason I refused to get back into running. Up until just recently, morning winter runs were the bane of my existence. I would rather squeeze a run in at the gym during my lunch break than feel the dark sting of a winter breeze against my cheeks.

And yet, the miracle of human agency means that I can and did learn how to exist in those chilly environments semi-comfortably. I doubt I’ll ever love a winter run, but because of what I know now, I no longer fear them. This article is a description of what I’ve learned and how I’ve applied that knowledge in my quest for a safe, warm, and dry winter run.

<h3>The Scientific Background - Mechanics of Heat Transfer:</h3>

Heat is energy, and energy loves to move. Energy transfers, in general, from high energy systems to low energy systems, and heat energy does the same. Heat flows from a warmer object to a cooler one. Cold is simply a lack of heat, so feeling cold is the experience of your body losing heat energy quicker than it can replace it.

Heat is transferred to and from the body in four main ways: conduction, convection, evaporation, and radiation.

- Conduction: Heat transfers via direct contact. When you hold a snowball, heat will leave your hand and enter the snow. The difference in temperature between your hand and the snowball determines how quickly the heat moves from your hand to the snowball.
  - Convection: Heat transfers to or from a fluid (liquid or gas) flowing across a surface. Your body will lose heat rapidly when cold air blows past it. The air rapidly picks up your body’s heat and moves it away. The movement maintains the difference in temperature between your skin and the air thus sustaining rapid heat transfer.
  - Evaporation: Sweat uses heat energy to change states of matter, removing body heat from the skin. Evaporation occurs more rapidly in dry environments; thus, your body can maintain a normal temperature more effectively in hot and dry environments than in hot and humid ones.
  - Radiation: Electromagnetic waves transfer heat “remotely” from one thing to another. The sun is the only significant radiant heat source in cold outdoor environments, with the body being another minor source of radiation.

<h3>The Environmental Context - Where Does Heat Come From?</h3>

Heat typically starts with the sun. Radiant heat enters the atmosphere and begins to burn everything up: the ground, the air, your car door handle, your exposed neck, etc. But in the winter, the sun’s radiation won’t do you much good. You might be able to rely on an external source of heat—the radiant heat of a fire, a hand warmer conducting heat into your skin—but even those sources of heat are temporary at best. In the winter, the most reliable source of heat is your own body.

Your body constantly uses energy from the food you eat. It keeps your heart pumping, your fingers typing, your brain thinking, and your stomach digesting the crunch wrap you had for lunch. In particular, movement demands an outsized amount of energy. Sugars and fats are broken down into energy molecules that split like miniature atom bombs every time a muscle needs to contract. The energy from that tiny explosion fuels movement, but, on average, 75% of the energy produced for movement dissipates as heat. The excess heat leaves the muscle tissue, enters the blood, and rushes around the body keeping everything at a comfortable 37° Celsius. If your body starts sensing that things are a little too warm, it expels heat via evaporation and conduction at the skin. On the other hand, if the muscles’ excess energy isn’t enough to maintain the body’s preferred temperature, your body can’t do much to compensate.

Despite all the marvelous evolutionary adaptations the human body can use to respond to extreme environments like heat or high altitude, when it comes to cold, we can only adapt our behavior.

<h3>Practical Applications - How to Behaviorally Adapt to the Cold:</h3>

Staying warm in winter environments revolves around preserving body heat. The body is your only reliable source of heat, and keeping that heat from disappearing into the winter horrorland around you is your ticket to a safe, warm, and dry winter adventure. So how do you keep all the heat in?

Let’s go back to the main methods of heat transfer and use those as a foundation for building out a body heat-preserving system.

- Conduction: Wear a thick insulating layer—a layer that your body can dump heat into without that heat immediately leaving out the other side. The best insulating layers will be large/high-volume clothing items. To entertain you with math for a second, increasing the size of an object increases its volume far more rapidly than it increases its surface area. A larger volume means more room for heat retention, a small surface area means less area for conduction to occur. Thicker clothing is warmer clothing.
  - Convection: Wear a wind- and water-resistant outer layer. This layer will keep the cold air from passing over your skin thus preventing convection from sucking up your body heat.
  - Evaporation: The benefits of a water-resistant outer layer extend beyond the practical benefits of preventing snow or rain from getting in. A water-resistant layer also increases the humidity inside your layers by preventing water vapor from escaping. Higher humidity environments prevent evaporation from occurring thus limiting sweat’s ability to cool your skin. That said, water and sweat retention isn’t always ideal either because water can also cool rapidly when given the chance. Wear a sweat-wicking base layer to keep the sweat moving away from your skin. Consider allowing your layers to ventilate from time to time—temperature allowing—to prevent your base and insulating layers from retaining excess moisture. 
  - Radiation: You can still use the sun, even in the winter, to stay warm. Dark outer layers can maximize the amount of heat you’ll retain from radiation. While not an especially effective method of heat retention at night, dark outer layers should have their place in sunny winter adventures.

In summary, rely on the three-layer method.

1. A dark, wind-resistant, and water-resistant outer layer. 
2. One or more thick insulating layers.
3. A moisture-wicking base layer.

<h3>My Personal System – Staying Safe, Warm, and Dry:</h3>

While the prior recommendations translate easily into top and bottom clothing choices, I’d recommend investing in a few additional items.

<b>Footwear:</b> My choice of socks and shoes will change depending on my thirst for adventure. For a brief run in light snow, I rely on a water-resistant trail shoe that I trust not to kill me the moment I step on a bit of ice. If it’s particularly cold or if I’m planning to be out for more than an hour, I’ll add an extra pair of thick socks as an insulating layer. The body will limit blood flow to cold extremities, and I don’t want to play around with frostbite. When I plan an adventure in deeper snow, I use a pair of insulated and waterproof overshoes or boots.

<b>Gloves</b>: For gloves, I start with a basic pair made from sweat-wicking polyester. I personally avoid using knit gloves as a first option unless it’s very dry outside. If things get excessively cold or windy, I add a pair of gloves that carry both insulation and wind protection duties. I like to carry multiple pairs of gloves and cycle them through as needed. I prioritize keeping my hands warm and dry. Again, frostbite is no joke.

<b>Headgear</b>: At present, I default to a synthetic balaclava that I can adjust as needed and then add a knit beanie as temperatures drop. I top it off with a jacket hood or two if the morning air has an extra bite to it. The nose is another frostbite prone area, so once the temperature or windchill is well below freezing, I will opt for a buff or even a full-face ski mask. Once the sun’s out, I add a pair of sunglasses or ski goggles because eye protection matters more with snow on the ground.

<b>Layering</b>: I am always prepared to add or remove layers. I will absolutely leave the house looking like I’m ready for an all-day ice climbing adventure in the arctic circle if it means making those first ten minutes or so more bearable. And once my body starts producing all that excess heat from moving, I may shed a layer or two. Or I’ll keep it all on and call it heat training ;)

<h3>Additional Considerations – What If It’s Not a Run?</h3>

For activities that require a lot of stopping and starting or include an overnight component, factors like moisture control, fabric choices, and flexible layering all become more important considerations.

<b>Moisture Control</b>: Running with a stack of layers can be a very sweaty activity. If the run is continuous and temperatures don’t vary much, that’s not necessarily a bad thing. Damp clothes will come off as soon as the run’s over, and no one needs to give wet clothes a second thought.

When activities require shifting energy demands—switching from scrambling through difficult terrain to meal stops—sweat rates can rapidly increase or decrease and accumulated sweat can turn cold fast. With too much sweat, insulating layers could soak and become a useless soggy mess. To manage sweat accumulation, avoid sweat as much as possible by dialing in exactly what layers are needed and use layers that won’t encourage the sweat to stick around longer than it needs to.

Moisture becomes a major concern when camping in cold conditions. Allow for some ventilation through your sleeping area to avoid moisture accumulating and freezing. Never go to sleep in wet clothes! Use wool or synthetic base layers to keep your body dry while you sleep. Use hand warmers, a warm water bottle, and/or other external sources of heat to help stay warm through the night without over-layering.

<b>Fabric Choices</b>: I can layer up for a run haphazardly in almost any situation and be okay assuming I follow the three-layer rule. My base layer doesn’t need to wick sweat perfectly, my insulating layer can be an old sweatshirt or two, and I don’t always need my shell to be water-resistant. I can be comfortable with the basics. More adventurous expeditions require more purposeful decision making.

Base layers need to be made of a material that someone intentionally designed to move sweat away from the skin. Synthetic fabrics or merino wool are the two best choices. Insulating layers should prioritize volume without overdoing the weight. Down or synthetic down is great for this because it has an incredible weight to volume ratio or “loft.” Outer layers need intentional water-resistance. Any old coat may keep the wind off, but it takes a bit of money to find something that will breathe and keep things dry after a celebratory snow angel.

<b>Flexible Layering</b>: More layers win when the winter adventure gets longer and more involved. I love having the ability to add or remove a layer of insulation as I move from a shady valley onto a hilltop blasted by sunlight. It’s not enough to assume that “you’ll warm up as you get moving” because you’ll also need to manage a sudden change in wind, an unexpected snowstorm, or nighttime temperatures 40 degrees lower than what you hiked in with.

Comfort in more adventurous scenarios than my meager runs require more thought, more research, more gear, and a fair bit more money. But the payoff can be worth the price. The silence and beauty of an aspen forest buried in a fresh coat of snow is hard to beat. It’s all a matter of doing the extra leg work before you get there.

<h3>Conclusion:</h3>

Running in the winter doesn’t need to be the dreaded nightmare I once imagined it to be. If you layer up properly and retain as much body heat as you can, you may find some small joy in the beauty of your own personal winter wonderland.

<h3>References:</h3>
I sourced all the science from Dr. Marcus Lawrence's lecture notes at Southern Utah University during the Spring Semester of 2025: <a href="https://drive.google.com/drive/folders/17zW9VHbRNSvCP3xAKUd6u4XIys37Ki7p?usp=sharing">Extreme Environments and Thermoregulation</a>

HomebrewHappiness

Safe, Warm, and Dry - The Mechanics of Winter Heat Loss and Retention

Homebrew
Happiness