One ski jacket carries 20,150 mm. Tested under another standard, the same jacket carries 23,000 mm. Here is how the numbers are produced, and how far to trust them.

The coldest four minutes of your ski day are the ones when you aren't skiing at all. They happen on the chairlift: sitting still, boots hanging in open air, wind finding every gap, legs generating no heat. Most people dress for the forecast low. They nail the chairlift and ruin everything else, because by the second run they're damp, and damp is what makes you cold. Most advice on how to layer for skiing comes in seasons. You don't ski a season, you ski a Tuesday. So: what each layer is responsible for, a conditions table you can check over breakfast, how your layer plan sets your jacket size, and, if you're in a one-piece suit, why the maths changes. And the most common way to get this wrong isn't wearing too little. It's wearing a fleece under a jacket that's already insulated. If your question is simply what to wear under a ski jacket, the short answer is three layers: a base layer, a mid layer, and your shell. The short version Set your baseline for the chairlift, not the run. You can only remove warmth mid-day, never add it. An insulated jacket already contains your mid layer. Below about −10°C (14°F), add a fleece. Above that, don't. Why Layering Beats One Big Coat The three jobs your outfit has to do at once One heavy coat has to do three incompatible things: move sweat off your skin, hold still air against your body, and stop wind and snow. Thick insulation is excellent at the second and bad at the first. The warmer it is, the sooner you sweat into it, and the less of that sweat escapes. Split the jobs and each garment gets to be good at one. The base layer is thin, and its only job is moving moisture. The mid layer is the lofty one, and it's the piece you take off. The outer layer just takes the weather. Add or remove the middle and the same two garments cover a 20°C swing. What actually makes you cold: sweat, wind and stillness Water conducts heat away from your body around 25 times faster than still air (cold-weather physiology review). That one fact explains most of what follows, including the ban on cotton. Wind strips the warm boundary layer your insulation just built. Stillness, meaning a queue, a chair or a long traverse, switches off the furnace. Temperature is the number everyone checks and the one that matters least. Still, dry air at −10°C (14°F) is easier to dress for than +1°C (34°F) in wet snow with wind behind it. The chairlift problem, and why it should set your baseline Jonas was at Val Thorens in the second week of January, −13°C (9°F), not a cloud. Heavy fleece under an insulated jacket, because that's what the forecast said. The first run was perfect. By the bottom of the second he could feel it between his shoulder blades: that first damp patch. Then ten minutes on the chair, and the patch went cold against his ribs. He spent the rest of the morning too hot going down and freezing going up, two different failures from one decision made at 8:15 in the car park. Set your baseline for the moments you're still. Then plan to shed. How to Layer for Skiing: The Three-Layer System, Layer by Layer The ski layering system has three parts. The three layers for skiing are a base layer that moves sweat off your skin, a mid layer that traps warm air, and an outer layer — your ski jacket and ski pants — that blocks wind, snow and rain. They let you add or shed warmth all day. Layer Its only job Best materials The usual mistake Base Move sweat off your skin Merino wool, polyester Cotton T-shirt, or two base layers Mid Trap a layer of warm air Fleece, synthetic fill, down Wearing it under an insulated jacket Outer Block wind, snow and rain Waterproof-breathable shell fabric Buying it to fit over a T-shirt Base layer: the moisture layer The base layer doesn't keep you warm. It keeps you dry, which is the precondition for warm. It should fit close, second skin rather than relaxed, because fabric that isn't touching you can't wick. Merino or synthetic is a genuine coin toss, and REI's experts lean merino: it resists odour, insulates when damp, and stays bearable on day three of a trip. Synthetic dries faster, costs less and survives a rental boot room. POWDER lands in the same place on multi-day trips, and both agree on the rule that matters more than the fibre debate: nothing cotton next to skin. Merino for slow days; synthetic for spring, hard laps and kids. Weight matters more than fibre: 150 gsm for spring and high output, 200 gsm for most winter days, 250 gsm and up for real cold. If you are building the layer from scratch, start with our merino and synthetic base layers. A 200 gsm merino piece such as the Ice-woven merino thermal underwear covers most winter days. Mid layer: the warmth layer Warmth is trapped air, and the mid layer's only job is to hold it. Fleece is the default: cheap, breathable, warm when damp, in roughly 100-weight (active days) and 200-weight (cold days) thicknesses. Lightly filled synthetic jackets pack smaller for the same warmth. Down is warmest per gram and the worst choice in a damp climate, since wet down stops working until it's dry, which on a coastal three-day trip may never happen. Outer layer: your ski jacket This layer takes the abuse, so it's where the fabric engineering lives. You need two separate properties: keep liquid water out, let water vapour out. NANEND's own shell fabric, for example, is an 88% polyamide / 12% polyurethane build, a tight, abrasion-resistant face bonded to a membrane (source: NANEND NAN SKIN fabric documentation). Three features matter more than any spec number: pit zips you can reach with gloves on, a hood that fits over your helmet, and a powder skirt that seals snow out at the waist. Doubling the base layer Two thin base layers don't make a warmer outfit. They compress each other, slow moisture movement, and leave a wet layer pressed to your skin. If you're cold, add loft in the middle, not another sheet against your body. Common mistakes, named outright: A cotton T-shirt anywhere in the system Two base layers "for extra warmth" A fleece under an already-insulated jacket Two pairs of socks in one boot Jeans or joggers under ski pants A jacket bought to fit over a T-shirt Browse mid layers → Match Your Layers to the Jacket You Have Your plan isn't abstract. It starts with the outer layer you already own, because that garment decides how much warmth you build underneath it. If it's a shell: you build all the warmth yourself A hard shell has no insulation. It's a weather shield and nothing more: the most flexible thing you can own, and the easiest to get wrong. Under a shell you're committed to base plus mid on every cold day, and a shell over just a base layer at −8°C (18°F) is a cold day, full stop. The upside is spring, where you strip to base plus shell. If it's insulated: don't double up An insulated jacket already contains your mid layer. That's why so many skiers say they "run hot" when what they do is wear a fleece under a filled jacket. On a normal winter day: base layer, and that's it. Add a light fleece only below about −10°C (14°F), or if you sit still a lot, or if you're doing slow laps with a beginner. Warm in the car park means overdressed, so take something off before you load. NANEND's Prismatic Series insulated jacket is typical of the category: warm enough to ski over a single base layer all season. If it's a 3L: check where the insulation sits before you choose a mid layer "3L" describes how the fabric is built, not how much fill is inside. Some 3L jackets have none; others have fill panels across the chest and back only, with sleeves and sides unlined for breathability. Partial fill means you dress it like a shell with a head start, not like a puffy. Where to go deeper One buying note, and then we're back to layers: waterproof figures only compare within the same test method. The same fabric reads 20,150mm under GB/T 4744-2013 and 23,000mm under JIS L 1092:2009 (source: NANEND's official buying guide) — different rulers, not different fabrics. Whichever number a brand quotes, it doesn't change what you wear underneath. If you're still deciding between hard shell, insulated and 3L, our full ski jacket buying guide covers the numbers in detail. How to Dress for Skiing in Five Conditions Cold and dry — high alpine and continental winters High alpine resorts, interior snowpacks, −12°C (10°F) and below. Cold is the easy part here; moisture is the hard one, because you still sweat on the descents. Run a midweight or heavyweight merino top and bottoms, a 200-weight fleece, and a shell. Open the pit zips at the bottom of every run and close them before you load. Wet snow and rain — coastal ranges and lower elevations Coastal ranges, lower resorts, anywhere hovering around 0°C (32°F). The hardest condition on the list, because water comes from both sides: rain outside, sweat inside that cold wet fabric won't move. Drop insulation and prioritise staying dry. Lightweight synthetic base, light fleece or none, fully waterproof shell with the hood over your helmet. Pack a dry base top. How to layer for skiing in spring and late season Spring is the condition people dress worst for: +5°C to +12°C (41–54°F), heavy wet snow by 2pm, sun that feels nothing like the thermometer. Lightweight synthetic base, no mid layer, shell with the vents open from run one. A vest is the smart spring mid layer, since it warms your core without cooking your arms. Start the day slightly cool. Anna's last day of the season was the last Sunday in March, a resort at 1,800m where the snow had gone to slush by eleven. She dressed for the winter she'd been skiing all season: full kit, heavy fleece. By the second run her back was wet through. She spent the afternoon skiing with her jacket unzipped to the sternum and her lens fogged, which works fine right up until you get on a chair. The fix costs nothing. The fleece stays in the car. Storm days and chairlift-heavy days A storm day is about sealing, because wind finds cuffs, neck and hem. Midweight merino, fleece plus a light puffy (or an insulated jacket), hard shell with a real storm hood. A shell like the Skyline PRO hard shell earns its keep here, and it's worth knowing what a RECCO reflector does before you duck off-piste. A chairlift-heavy day is the opposite: short runs, slow queues, long exposed rides. You want warmth you can remove, so go insulated jacket or shell plus a packable puffy, with the mid layer riding in a ski backpack rather than on your back. What to wear skiing in five different conditions Use this matrix to pick your three layers before you leave — it covers every forecast you'll realistically ski in. Condition Base layer Mid layer Outer layer Key move Cold & dry, −12°C (10°F) and below Midweight or heavyweight merino top + bottoms 200-weight fleece or light synthetic jacket Shell jacket; shell or insulated pants Vent at the bottom of every run, close before the lift Wet snow or rain, ~0°C (32°F) Lightweight synthetic, fastest drying Light fleece or none Fully waterproof shell, hood over helmet Prioritise staying dry over staying thick Spring / late season, +5°C to +12°C (41–54°F) Lightweight synthetic None, or a packable vest Shell jacket, vents open from run one Start slightly cool; shed early Storm day, heavy snow and wind Midweight merino Fleece + light puffy, or an insulated jacket Hard shell with full storm hood Seal cuffs, neck and hem Chairlift-heavy day, long lifts and slow queues Midweight merino Removable mid layer you can carry Insulated jacket, or shell + packable puffy Put the mid layer back on before you load The Lower Half: What to Wear Under Ski Pants and Boots Your legs work hard on every turn, go cold first on a chair, and spend the day inside a plastic boot that doesn't breathe. Base layer bottoms: when, and what weight Below about −5°C (23°F), or on any day with long lifts, wear them. Above +2°C (36°F) most people are better without. Midweight covers most of the season; heavyweight is for deep cold and slow days. Do you need a mid layer on your legs? Usually not, since legs generate plenty of heat and have the biggest muscles doing the work. Mid layer bottoms suit people who run cold, very slow days, or anyone standing around teaching a beginner. If you need leg insulation, buy insulated pants rather than adding a layer that bunches behind your knee. Shell pants, insulated pants or fleece-lined — pick by temperature Shell pants plus base layer bottoms is the flexible setup that works across a season. Insulated pants are warmer and simpler. Fleece-lined sits in between and is the easiest recommendation for anyone who runs cold or skis mostly in resort, and NANEND's fleece-lined loose fit pants are built for exactly that. The full trade-off is in our ski snow pants buying guide. One pair of socks, above the boot cuff One pair. Over the calf, thin, made for skiing. Two pairs compress the liner, restrict circulation and make your feet colder, which is the opposite of the goal. Socks aren't insulation; they're moisture transport for the one part of you that can't be vented. A dedicated ski sock is worth the money: see our ski socks built for boot cuffs. If you are weighing fibres, merino vs synthetic ski socks goes through it in detail. Layering Under a One-Piece Ski Suit A suit changes the maths, and not in the way you'd expect. Worth knowing: this section is about true one-piece suits, where the top and bottom are a single garment. A matching jacket-and-pants set is not the same thing, and it layers exactly like the combination described above. Why a suit changes the layering math With a jacket and pants, warmth leaks at the waist every time you bend, fall or reach. A suit has no waist seam at all, so no gap, which makes it measurably warmer than an equivalent two-piece in wind and deep snow. The trade-off is ventilation. A jacket lets you unzip and dump heat through your core; a suit gives you fewer places to do that. You have to get base and mid right first time, because you can't fix overheating on the lift. How to layer a ski suit for a cold day versus a mild day Cold day: midweight merino top and bottoms plus one light fleece. That's it. Don't put a bulky mid layer under a suit, or you'll lose shoulder mobility and won't be able to vent it later. Mild or spring day: lightweight synthetic base, no mid layer. A suit runs warm by design, so skip it on those days if you own a two-piece alternative. Bathroom breaks and mid-day venting A one-piece means a full upper-body undress at every bathroom stop. On a cold day with a six-year-old, that's not a small thing. Group days that stop often favour a two-piece; hard skiing from first chair to last favours the suit. For venting, use what you have: front zip, leg vents, and above all the neck. Opening the collar is the fastest heat dump on a suit. Who a suit actually suits People who ski deep snow, fall a lot, hate snow down their back, or like getting dressed in one move. Less ideal for lesson days, warm spring conditions, or anyone who sheds a layer every hour. If you're weighing a suit against a jacket-and-pants setup, the ski suit sets collection is the place to compare — the layering logic above applies either way. Fit: Why Your Jacket Size Depends on Your Layer Plan The size on the label only means anything once you've decided what goes under it. Try it on wearing exactly what you'll ski in Never buy a ski jacket over a T-shirt. Wear your base layer and the thickest mid layer you own. Sounds obvious; almost nobody does it, which is why so many ski jackets are one size too small in February. Four movement checks before you commit Do all four in the changing room: Overhead reach — both arms straight up. The hem shouldn't rise above your belt line. Hug and reach — arms crossed, reaching forward. You should feel fabric across the back, not tension. Squat — deep, knees bent. Nothing binds at the shoulder or pulls at the hem. Cuff-to-glove overlap — arms forward. The cuff must cover the back of your glove wrist with room to spare. Fail any one and the jacket fights you all season, however good the fabric is. Sleeve length, hem length, and helmet clearance Sleeves should end past the wrist bone, around the base of your thumb. The hem should cover your waistband standing and reaching. Check the hood with your helmet on, because a hood that won't go over the helmet is a hood you'll never use, which leaves your neck as the weak point. Shell versus insulated: which needs more room, and why A shell needs more room, since all your warmth goes underneath it. An insulated jacket should fit closer, because the fill is already inside and buying it too big means heating empty air. If you own both, expect different sizes and don't let it bother you. NANEND's Skyline NOVA collection runs XXS to XL. How to Layer Kids for Skiing Why kids swing from hot to cold faster than adults Children have a much higher surface-area-to-mass ratio than adults, so in cold conditions they lose heat faster. Size isn't the only factor: a child's metabolic heat does rise more than an adult's in the cold, but that extra heat is enough to hold body temperature during exercise and not during prolonged rest, which is exactly what a chairlift ride is. Add to that less judgement, since a cold kid will often say nothing until they're properly cold. Check them at the bottom of every lift, not three hours later. The kids' three-layer setup — and the one layer parents skip Base, mid, outer, same as adults. The skipped layer is the mid one, usually because the jacket they bought is already insulated. On a cold day that isn't enough, since kids sitting still lose heat faster than you do. A light fleece in the pack, on before the lift and off before the run, is the highest-value thing you can add to a child's kit. Ski Utah's guide agrees on the basics: layers, dry hands, no cotton. Growth room without the baggy penalty Buy slightly big, yes. Two sizes up, no, because an oversized jacket leaves air gaps the body has to heat, and the cuffs swallow the gloves, which is how snow gets in. One size maximum, with cuffs and hem adjusted snug where it matters. If you are kitting a child out from zero, the kids' ski layers collection shows the whole system in one place. Mittens, neck gaiter, and the always-pack-a-spare rule Mittens, not gloves, for anyone under about ten: fingers sharing a space stay warmer than fingers in separate ones. A neck gaiter covers the gap a collar leaves on a small neck. Pack a spare of everything touching skin. Kids find water, which is where our youth ski goggles and the accessories collection come in. Marko's first day out with his six-year-old was a bluebird morning at a small family resort in the Dolomites, warm enough that he nearly left the spare fleece in the car. He didn't. By 10:30 the boy had fallen twice in wet snow and the fleece he was wearing was soaked through at the cuffs. Marko swapped it in the lift queue. That's the whole difference between a day that ends at 10:45 and a day that runs to lunch. Hands, Neck, Head and Eyes: The Parts That End the Day Early Your core can be perfectly dressed and you'll still quit at 1pm because of a gap the size of a coin. Neck gaiter or balaclava — pick by wind, not by temperature Your neck is a large, hot blood vessel under thin skin. A gaiter is right for most days; a balaclava is for wind, storm days and chairlifts facing into the weather. Choose by how much air is moving, not by the thermometer. Both should tuck into the collar, not sit on top of it. Gloves versus mittens, and the liner trick Mittens are warmer; gloves are more dexterous. If you run cold, go mittens. Better still, wear a thin liner glove underneath, which gives you dexterity for buckles and warmth the rest of the time. Dry hands matter more than thick hands: a wet glove at −5°C (23°F) is miserable regardless of fill. Goggles and helmet: the gap problem The gap between helmet brim and goggle top edge is the most common cause of a cold forehead and fogged lenses, so try them on together, in the shop. Photochromic lenses like NANEND's NG23MAX solve the other half, because you stop swapping lenses every time the light shifts. Fit detail is in our ski goggles buying guide and ski helmet buying guide; browse snow goggles and ski helmets if you're replacing either. Where your shed layers go Layers only work if the ones you remove have somewhere to go. Ten to eighteen litres is plenty for a resort day: the fleece for the chair, a dry base top, water. Anything bigger is a nuisance on the lift. Running Your Layers During the Day You'll change your layers four or five times before lunch. Plan for that. Vent before you sweat, not after The instinct is to wait until you're hot. By then you're already damp, and damp takes about twenty minutes to shift even with everything open, which is why you should be reaching for the pit zips at the bottom of the first run, while you still feel fine. Close everything before you sit down. What to do with the layer you take off Never tie it round your waist, since it ends up under your hem, exactly where snow gets in. Roll it into the pack, or use a base locker and time your shed around a lift that passes it. What to wear skiing: the car-park checklist Tick these off before you leave the car park, in this order: Base layer top, no cotton anywhere Base layer bottoms below −5°C (23°F) One packable mid layer Shell or insulated jacket, seams sealed One pair of over-calf ski socks Neck gaiter or balaclava Goggles matched to the helmet Mittens or gloves plus liners Spare dry base top in the pack Multi-day trips: drying overnight Base layers won't dry in a cold hotel room. Hang them near a heat source, never on it, turn them inside out in the morning so yesterday's moisture sits on the outside, and rotate two tops rather than trying to dry one. Outer layers need far less attention: NANEND's own guidance is to wash technical shells once or twice a season (source: NANEND official buying guide), because over-washing does more damage than normal use. Frequently Asked Questions What are the 3 layers for skiing? A base layer that wicks sweat off your skin, a mid layer that traps warm air, and an outer layer, meaning jacket and pants, that blocks wind, snow and rain. You add or remove the mid layer to match conditions. Merino or synthetic base layer — which is better? Merino wins on multi-day trips and low-output days; synthetic dries faster and costs less. On merino vs synthetic, neither beats the other outright, and both beat cotton. Why is cotton bad for skiing? Cotton holds moisture against your skin instead of moving it outward. Water conducts heat away from your body around 25 times faster than air, so a damp cotton tee on a windy chairlift gets you genuinely cold. What should I wear under an insulated ski jacket? Usually just a base layer. The jacket's fill already does the mid layer's job, so a fleece underneath is the most common cause of overheating. Add one below about −10°C (14°F), or if you sit still for long stretches. What should I wear under a shell ski jacket? A base layer plus a mid layer on every cold day. A shell has no insulation of its own, so warmth is entirely up to what you put under it. On warm spring days, drop to base plus shell. How many layers under a ski jacket at −10°C / 14°F? Three: a midweight or heavyweight base layer, one mid layer, and your shell. With an insulated jacket, two, meaning base plus jacket, adding a fleece only if you run cold or sit still a lot. What do I wear when it's raining or the snow is wet? Prioritise staying dry over staying thick. Lightweight synthetic base, minimal or no mid layer, fully waterproof shell with the hood over your helmet. Carry a dry base top. Should I size up my ski jacket to fit layers underneath? Only if you're buying a shell. Try it on wearing the layers you ski in, then run four checks: overhead reach, hug-and-reach, squat, and cuff-to-glove overlap. An insulated jacket fits closer. Do I need base layer bottoms for skiing? Usually not, since legs generate plenty of heat while skiing. Choose insulated or fleece-lined snow pants for cold days instead of adding a layer that bunches behind the knee. What do you wear under a one-piece ski suit? A base layer top and bottoms, plus one light mid layer on cold days. Skip bulky mid layers, because a suit has fewer venting options than a jacket and overheating is harder to fix later. Is a ski suit warmer than a jacket and pants? Yes. There's no waist seam for wind and snow to enter, and no gap opening up when you bend or fall. It's less convenient for bathroom breaks and venting, so it suits deep snow over lesson days. How many layers does a child need for skiing? Three, same as an adult, and the mid layer is the one parents most often skip. Add a fleece before chairlift rides, check hands and neck at the bottom of every lift, and pack spares. Build Your System Jonas's mistake wasn't buying the wrong jacket. It was dressing for the coldest number on the forecast instead of for the shape of his day. Everything above comes down to one habit: dress for the minutes you're standing still, and build the rest in pieces you can take off. Check the matrix before you leave, because the right answer in the Alps in January is the wrong answer on a coastal range in rain. That is what knowing how to layer for skiing actually buys you: a system you can tune all day. Work from the outside in: hard shell ski jackets, insulated ski jackets, mid layers, or the full ski jackets collection. Those 25 models, from $176 to $480, cover every conditions plan in this ski layering guide. Written by the NANEND product team · Last updated: October 2026 How we built this guide: the condition recommendations come from our own fabric reports and published cold-weather physiology research. Names and conditions in the examples above are composites drawn from a few seasons.

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