Mid-layer = cold weather clothing?
When choosing clothes for mountain climbing or other outdoor activities, it is said that the important thing is to keep in mind "layering."
Basically, it means wearing three layers of clothing with different functions: "base," "mid," and "shell," which allows you to move safely and comfortably even in harsh conditions with drastic environmental changes. In this article, we'll take a look at the "mid layer," which plays a slightly more complicated role in layering
A mid-layer is a garment worn between the so-called undergarment (base layer) and outer layer (shell layer). When I first started climbing mountains, I simply thought of it as "cold weather clothing?", but it's not as simple as just keeping you warm and feeling comfortable. A variety of elements and functions are required to provide optimal warmth and comfort in all conditions. As proof of this, even though it's simply called a mid-layer, the optimal way to wear it varies depending on the season, purpose, effect, etc., depending on the fabric material, shape, thickness, etc
As you climb mountains for longer periods, you will often find that one type of mid-layer is not enough to deal with the situation, as it can be too cold or too hot, too humid or too breathable, too heavy, too bulky, etc. In that sense, mid-layers are a very complex subject, or perhaps a tricky mountain wear that can make even beginners cry
So, this time we will introduce the best mid-layer models to suit a variety of situations, as well as some tips on what to look for and what criteria to use when choosing the perfect piece for you
table of contents
- [By Type] 7 Recommended Mid-Layers You'll Never Let Go of Once You Try Them
- Down insulation (spring-fall): Black Diamond Deploy Down 0.5 Full Zip Hoodie
- Down insulation (winter): Rab Mythic G Jacket
- Synthetic insulation for warmth (spring to autumn): milestone Heatwave Titanium Hoody
- Warm synthetic insulation (winter): Rab Cirrus Ultra Hoody
- Active Insulation (Lightweight): Arc'teryx Delta Hoody / Rab Evolute Hoody / Patagonia Nano Air Ultralight Full-Zip Hoody
- Active Insulation (Heavy): Teton Bros. Sub Hoody / Rab Xenair Alpine Flex Jacket
- Year-round fleece: Patagonia R1 Air Jacket
- How to Choose: Tips for Choosing Your Mid-Layer Wisely
- summary
[By Type] 7 Recommended Mid-Layers You'll Never Let Go of Once You Try Them
As someone who has been following the evolution of mid-layers for many years, I have chosen the models I personally use and would like to give my seal of approval to, both thin and thick. This list is largely based on personal preference, so please use it as a reference only
Down insulation (spring-fall): Black Diamond Deploy Down 0.5 Full Zip Hoodie
As of 2025, this is one of the world's lightest down hoodies (full-zip jackets), making it useful year-round, not just in winter. Made with 1000FP premium goose down and a 4-denier shell fabric, it's surprisingly light at just 160 grams. Taking full advantage of down's incredible lightness and compactness, this model is sure to be a valuable ally for any mountain enthusiast seeking maximum warmth with minimal weight. In addition to this full-zip hoodie, there's also a web-exclusive pullover hoodie that's incredibly light at just 148 grams
Although it is made with the highest quality down, the amount of down is minimal, so it may not provide sufficient protection against the cold in the middle of winter, but it will be the perfect talisman for mountain climbing from spring to early winter, when temperatures change drastically depending on the weather and it is difficult to predict what equipment to bring
Down insulation (winter): Rab Mythic G Jacket
Rab Mythic G Jacket is a winter down jacket perfect for active mountaineers and hikers seeking lightweight comfort while maintaining the highest possible level of insulation. This is the ultimate masterpiece from Rab, the self-proclaimed "master of insulation." It boasts a premium 1000FP loft and an ultra-thin 7D Atmos™ nylon ripstop exterior. The lining features Rab's proprietary "TILT Technology," where every fiber is individually coated with titanium. This significantly reduces radiant heat loss and maximizes thermal efficiency without sacrificing breathability. Its warmth is instant, yet its light weight of less than 300 grams and compact size—the size of a clenched fist—makes it undoubtedly one of the most portable winter garments for minimalists looking to keep their winter backpacks tucked away.
Synthetic insulation for warmth (spring to autumn): milestone Heatwave Titanium Hoody
This season's highly anticipated newcomer, the milestone Heatwave Titanium Hoody, . Featuring Climashield® insulation, which combines lightness with excellent insulation, and a titanium sputtered lining, it's a clever innovation that maximizes warmth despite its light weight. Unlike down, it's made of synthetic fiber, so it's safe for mountain climbing, where there's a risk of getting wet. It's a warm and insulated garment from spring to autumn, and can also be used as activewear during harsh winters.
Warm synthetic insulation (winter): Rab Cirrus Ultra Hoody
This tough winter garment prioritizes insulation and durability, offering warmth, comfort, and loft for the ultimate winter mountaineering experience. Its PrimaLoft® ThermoPlume® insulation is so light and fluffy it could be mistaken for down, and its high insulation quality is so impressive it's practically comparable to down. The Rab Cirrus Ultra Hoody, with its generous use of high-performance insulation, excellent warmth and ventilation, and practical pockets, is a versatile and versatile model perfect for winter mountaineering. Its compact storage makes it ideal for winter mountaineering
Active Insulation (Lightweight): Arc'teryx Delta Hoody / Rab Evolute Hoody / Patagonia Nano Air Ultralight Full-Zip Hoody
Active insulation, which has enhanced breathability and sweat-removal capabilities to reduce discomfort even in cold weather, is ideal for hiking and mountain climbing. However, even among these, for climbing in the autumn mountains, it's best to choose something that's not too thick (highly insulating), but also not too exposed and too windy, which can be cold. Therefore, it's best to choose something that's breathable, has moderate wind resistance, stretches for easy movement, and is as thin and lightweight as possible. Based on these criteria, our recommendations are listed below. The Arc'teryx Delta Hoody's OCTA and Delta Peak combination and the Rab Evolute Hoody's PrimaLoft Active Evolve and Motiv Aero combination are particularly excellent. If you prefer a little more wind resistance, the Patagonia Nano Air Ultralight Full-Zip Hoody is also convenient and can be used year-round
Active Insulation (Heavy): Teton Bros. Sub Hoody / Rab Xenair Alpine Flex Jacket
For activities like snowy mountain climbing and backcountry skiing in the dead of winter, which involve intense sweating in bitterly cold conditions, it's important to have a jacket that can keep out cold air and wind while still allowing sweat to escape. With that in mind, the basic lining should be Active Insulation, which combines heat insulation with breathability and quick-drying properties, and ideally, it should have a windproof and water-repellent outer fabric that provides moderate wind protection. Another excellent model we recommend, offering ample mobility around the shoulders and elbows, is the Teton Bros. Sub Hoody . It combines lightweight, breathable, highly insulating, and stretchable lining "Stretch OCTA" with a softshell outer fabric that offers high performance throughout, making it ideal for active outerwear. It's been a favorite of mine for the past few years, and I prefer the hoodless version for layering.
Another jacket that's equally recommended is the Rab Xenair Alpine Flex Jacket . It features a windproof, breathable, and stretchy Pertex Quantum Air outer shell, breathable Primaloft Gold Insulation Active+ insulation , and stretch fleece side panels, making it flawless down to the smallest detail. While it's not as breathable the Sub Hoody , it does a better job of blocking wind and cold air, making it resistant to the cold and perfect as an outer layer.
Year-round fleece: Patagonia R1 Air Jacket
Fleece holds a special place in the hearts of Patagonia. Developed long ago when animal fur sweaters were the only winter wear available, the creators of this revolutionary synthetic winter garment continue to bring new fleeces to the outdoor scene, warmer, lighter, and more user-friendly, even now, more than 40 years later. Patagonia's latest and most highly recommended fleece is the R1 Air. The R1 series is synonymous with technical fleeces favored by mountain athletes worldwide, and this model represents a major evolution of that classic
By deliberately abandoning the "versatility" of traditional fleece, this is an excellent technical fleece that offers optimal breathability, warmth, and a high level of comfort for more intense cold-season activities. The unique structure of the hollow-fiber jacquard fleece combines light weight, warmth, and breathability and quick-drying properties at an excellent level. I would definitely recommend wearing it over a base layer for trail running in autumn and winter, ski touring, climbing approaches, and fast-paced hikes in cold weather
This full-zip jacket, which debuted in the 2025 season, features three pockets: two zippered pockets on each side and a chest pocket. Its slim silhouette makes it versatile enough to be used as both a mid-layer and an everyday outer layer. When used as a mid-layer in cold weather, it exceeded expectations, maintaining comfort without being too hot or too cold. Its excellent balance of warmth, breathability, and quick-drying properties makes it practically active insulation. You can choose from a variety of styles, including crew neck and full-zip hoodies, depending on your preference
The elegant design, typical of Patagonia, makes it suitable for trekking, climbing, backcountry, and even everyday use in winter. Its versatility makes it a must-have for any winter outdoor activity. I personally don't see myself being without it 24/7 this winter, whether on or off the job
How to Choose: Tips for Choosing Your Mid-Layer Wisely
Tip 1: Learn about layering
Before we continue, let's briefly review the concept of layering (you can skip this if you already know what it is)
In the outdoors, "layering" refers to the theory of how to dress in order to stay as safe and comfortable as possible in harsh natural environments. Layering combines advanced functions that cannot be achieved with a single piece of clothing, such as quickly expelling moisture from clothing, mainly due to sweating, keeping the body dry and maintaining a constant body temperature (insulation), and blocking out outside air, rain, and snow. Layering does not simply mean wearing multiple layers of clothing; broadly speaking, it is achieved by layering layers (clothing) with the following three functions, in that order, starting from the layer closest to the skin
Base layer: absorbs sweat and transfers it to the outside
The layer worn directly on the skin is called the base layer. It absorbs sweat from the body and releases it to the outside (passing it on to the upper layer) so that it doesn't remain on the skin, keeping the skin dry and helping to maintain a constant body temperature, while also reducing the discomfort of sweaty clothing. For this reason, synthetic fibers and wool, which have excellent moisture-wicking and quick-drying properties, are the go-to fabrics for this. In hot weather, you'll often be wearing just this layer, and it's the piece of clothing you'll wear most often throughout the year
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Midlayer: Keeps you warm (and wicks away moisture)
The role of a mid-layer is simply to keep you warm (insulate). By sandwiching padded clothing between your body temperature and the cold air outside, it creates an "air barrier." This traps warm air close to the surface of your body, maintaining warmth and comfort. Another important role is breathability, allowing moisture (water vapor) released from the base layer to escape. Unfortunately, however, there is still no product that is always comfortable regardless of the season or activity. This is why it's important to choose your mid-layer wisely, as we'll explain in more detail below
Shell layer: Blocks wind, rain, snow, and air (and expels moisture)
While the base and mid layers primarily serve to keep the inside of the garment comfortable, the role of the shell layer is primarily to protect the inside from the external environment. It blocks out external stimuli that could threaten comfort, such as cold air, rain, wind, and snow, keeping the inside of the garment safe. Specifically, wearing a jacket made of waterproof and breathable material such as GORE-TEX prevents wind and water from entering from the outside while allowing moisture from the inside to escape. Depending on the expected weather conditions, there are various types of shell layers, from thin windproof types to thick types with high waterproof, windproof, and insulating properties
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Point 2: Know the main types of midlayers and their characteristics
Now that we understand the role of layering, we can finally get to the heart of choosing a mid-layer. As mentioned above, the main role of a mid-layer is to insulate and keep warm, but it's not as simple as just choosing a jacket with good thermal insulation
When climbing mountains, there are times when you are still and times when you are very active, times when it is just a little chilly and times when it is freezing cold. There is still no single garment that provides just the right amount of comfort in all situations
The simplest and smartest way to achieve just the right amount of warmth and comfort for all your mountain needs is to use multiple mid-layers with different capabilities
Typical midlayer #1: Down insulation
When talking about cold weather outdoor clothing, the first thing that comes to mind for most people is a down insulation jacket. It is made with feathers collected from waterfowl as the filling, and is sealed in with a highly windproof outer and inner fabric. When it comes to insulation against its lightness, no other material in the world can match it
However, while it has outstanding insulating properties, its weakness is that it can continue to warm you without you knowing how much, so it can get too hot and stuffy inside the clothing, making it uncomfortable. It's also important to note that if it gets wet, its heat retention ability drops significantly. However, in recent years, many down products have appeared that utilize the latest technology to overcome these weaknesses. In any case, it is undoubtedly the best winter clothing when you want to stay warm while staying still in extremely cold places or when you are not moving around much
Typical midlayer #2: Synthetic insulation (warmth-focused type)
The next most popular mid-layer material is synthetic insulation, a jacket filled with artificial padding, mainly made from polyester fibers, developed by humans as an alternative to down. Its unique feature is that it offers insulation per weight approaching that of down, while also being resistant to getting wet. Its toughness, which means it retains its heat retention even when soaked with sweat, rain, or snow, is an important advantage when outdoors, and the more strenuous the activity, the more situations in which synthetic insulation is useful. Another major attraction is its ease of care, as it is easy to wash. Typical padding materials include Thinsulate, Primaloft, Coreloft, and Exceloft
The heat retention of down has never been able to match up to that of down, but in recent years, it has been steadily improved thanks to high-tech materials such as aerogel, so there is no doubt that its performance and usability are continuing to improve
By the way, strictly speaking, recently there have been new paddings that are neither down nor synthetic, such as padding made from wool fibers, but for now I think it's okay to group them all together in this category
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Typical midlayer #3: Active insulation (for active wear)
The other, which was born as a derivative product of the synthetic insulation mentioned above and has become well established in recent years, is the next-generation mid-layer "active insulation" jacket
The material is the same as the previous synthetic fiber padding, and although it does not have the same heat retention per weight as the above type, it has better quick-drying and breathability, and has the properties of keeping the inside of the garment dry at all times even if you sweat
Many models also feature stretchability, making them suitable for more active scenes, and are surprisingly comfortable even when sweating and working up an intense workout in low temperatures, so you can wear them for long periods of time while you're active
The Active Insulation Jacket is a "cold weather garment that you can move in." Because it keeps you comfortable even when you're constantly wearing it during winter activities, it's now an indispensable mid-layer for not only winter mountain climbing but also backcountry adventures where it's difficult to put on and take off
Representative materials include Toray 3DeFX+, Patagonia Full Range, Polartec® Alpha®, THE NORTH FACE Ventrix™, and Primaloft® Gold Active, and new materials are constantly being introduced by various manufacturers
Typical midlayer #4: Fleece
Developed in the late 1970s as the ideal mountain sweater, it was warm but did not absorb moisture (it was quick-drying), and quickly became the go-to winter garment for outdoor use. Fleece clothing is still an indispensable item for us today
Fleece is a well-balanced outdoor cold weather garment that is light, warm, easy to move in, quick-drying, and retains its heat even when wet, but it has recently been facing fierce competition from other materials. This is because fleece is inferior to down in terms of weight, packability, and heat retention, and is also inferior to active insulation in terms of quick-drying and breathability
However, over the years of evolution, various fleeces have been created to suit diverse needs as technology has advanced, with some fleeces being windproof, others being less bulky, and others being more stretchy, so it would be a shame to dismiss fleece as a dead product just yet
Point 3: Match it to the timing and situation
Below is a table comparing the typical mid-layers mentioned above with their general features
Of course, performance will vary greatly depending on the individual characteristics of each product, the thickness of the fabric, and the quality and amount of padding, so please consider this as a guideline only
| kinds | Down insulation | Synthetic insulation (heat retention type) | Active insulation (for active wear) | Fleecewear |
|---|---|---|---|---|
| Thermal insulation material | down | Chemical fibers, etc | synthetic fibers | synthetic fibers |
| Insulation per weight | ◎ | ◯ | △ | ◯ |
| Compactness | ◎ | ◯ | ◯ | △ |
| Breathable and quick-drying | × | △ | ◎ | ◯ |
| Resistance to wetting | × | ◎ | ◯ | ◎ |
| Comfort | ◎ | ◯ | △ | ◎ |
| Ease of movement | △ | ◯ | ◎ | ◎ |
| Windproof | ◎ | ◎ | △ | △ |
| Easy to care for | △ | ◎ | ◎ | ◎ |
By referring to the comparison table above, you can narrow down the type of cold weather gear you need. As you can see, functionally, each type of cold weather gear is largely complementary, and one size does not fit all. For this reason, to ensure maximum safety and comfort, it is best to use different types depending on the situation, and the best option at the moment is to always carry two: a down jacket and active insulation. However, of course, there is no guarantee that this will always be possible due to budget or physical constraints, so it is important to determine what is important for each course and choose the clothing you will wear and carry with you. That is what makes choosing outdoor gear difficult, but also what makes it fun
However, for those who want a simpler answer, we have summarized the following two questions to help you choose the best mid-layer, although they may be a bit rough. Of course, please note that there are also versatile models in each category that combine many functions, so it is not possible to draw a clear line
Question 1: When should I wear it?
The first question to ask is, "Will you wear the mid-layer when you're stationary, or will you wear it when you're moving?"
If you plan on not moving (sweating) when wearing winter clothing, you have two choices: "down insulation" or "synthetic insulation (warmth-oriented type)." On the other hand, if you're outdoors in the winter and feel chilly whether you're standing still or moving, and want to wear it while you're active, you have two choices: "active insulation (type worn while active)" or "fleecewear."
Question 2: What are your concerns when wearing it?
Once you've chosen a mid-layer that will be useful when stationary, the next question to consider is, " Am I going to wear this when I'm not worried about getting wet, or am I going to wear it on a mountain hike where I might get wet ?" Depending on your choice, the following types will be derived:
| Wear it when you're stationary | |
|---|---|
| No need to worry about getting wet | Down insulation |
| There is a chance of getting wet | Synthetic insulation (heat retention type) |
When choosing a mid-layer to wear while on the move, it's a subtle difference, but you whether you prioritize breathability and quick-drying, or balance and comfort . We recommend choosing the following types for each.
| Wear it while on the move | |
|---|---|
| Sweating heavily | Active Insulation |
| Sweat a little | Fleecewear |
Point 4: Other important points to check when choosing winter clothing
From my personal experience, here are some points to keep in mind when choosing a mid-layer:
When using it as an outer layer, it is convenient to have hand warmer pockets on both sides, but if you are wearing it as a mid-layer, it is not necessary. In that case, a chest pocket is more convenient
Food
Having a hood or not makes a difference in whether or not you can keep your head warm. Naturally, a hood improves the ability to keep you warm when considered individually, but it's best to consider this in terms of the entire layering system if possible. For example, if your base layer, mid-layer, and outer layer all have hoods, it can create quite a lot of congestion around your neck, making you feel hot, bulky, and breathless. At the very least, you can consider that as long as your outer layer has a hood and you can keep your neck warm with a balaclava or something similar, that's enough. In that case, a jacket without a hood is sufficient as a mid-layer. I actually quite like this pattern
Most hats are made of stretch material that can be adjusted to fit your head size, or they can be adjusted with a drawstring. If they don't fit your size, they can be uncomfortable because they leak air or block your view. Also, winter clothing that is meant to be worn as outerwear is often made larger to be worn over a helmet, so preferences vary on this point
Outer fabric (whether to wear as outerwear or not)
When layering in the mountains, cold weather clothing is generally thought of as a mid-layer worn under a shell, but clothing made only of insulating materials like sweaters and fleece has the disadvantage of being difficult to use as an outer layer in the mountains, as it is light, breathable, and sweat-wicking. On the other hand, types with padding sandwiched between windproof, water-repellent shell fabric can be used as an outer layer, but when used as a mid-layer, one layer of shell fabric is wasted in terms of breathability. Neither is superior, so it is best to use them according to the purpose
summary
I've thought about my own best choices for choosing a mid-layer. Of course, this is merely an ideal, and it goes without saying that it's fun and important to be creative and create your own style with the limited equipment you have. In the outdoors, where "uncomfortable = dangerous," don't forget that there's a fine line between an unexpected snowstorm being a wonderful experience if dressed appropriately and a terrifying experience you never want to experience again if dressed incorrectly. I hope you can find the ideal mid-layer for you
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