Thermals, long johns, base layers – whatever you want to call them, there’s nothing like a warm layer worn next to the skin to help keep the chill of winter at bay.
Whether you’re off skiing, hiking or cold weather camping, layering up is the best way to trap in heat and keep cosy in the great outdoors – and a good layering system starts next to the skin with a quality base layer top and leggings set.
It’s definitely worth trying thermals on in person, especially if you’re on the tall or short side – they should hug your body without feeling too restrictive around the waistband, ankles, neck or sleeves. Some base layers are stretchier than others – we reckoned thermals with some stretch offered more warmth on test, as there’s no empty space between the fabric and your skin for the cold to creep in.
Thermal tops usually have a crew neck or a high, zipped neck – the latter can double up as a neck warmer, and some tops also sport hoodies for extra warmth.
We also look for base layers that use flatlock stitching, which means sewing raw ends together so there’s no bulky seam and avoids any rubbing against your skin.
Many base layers are made with synthetic materials such as polyester, but the best (but often the most expensive) base layers are made with 100 per cent Merino wool – Merino is very warm but still highly breathable, and is great at wicking away sweat. It also has naturally antimicrobial properties, making it perfect if you’re getting active or for when you’re heading into the backcountry without a shower in sight.
Bamboo base layers are more recent arrivals on the market – they’re also a great choice, as they’re soft to wear, antimicrobial and more eco-friendly to produce than synthetic materials. You may see base layers listed with a number, such as 140 or 220 – this refers to their weight in grams, and the higher the number, the warmer, but heavier, the base layer. We tested out the latest base layers on cold weather hikes and compared them for warmth, breathability and comfort.
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Montane primino half-zip top and trail series leggings
Meet Montane’s top-performing thermal combination. The 140g top is light and breathable but still provides surprising warmth thanks to a mix of Merino wool and Primaloft insulation (a brand of synthetic insulation that stays warm even when wet), while a covered zip neck provides extra ventilation. This was one of the most flattering tops we tried out, and looks good worn with jeans as well as hiking trousers. The thermal leggings are a versatile investment – they’re slim-fitting and warm enough to work as base layers but also excel when worn alone as trail running or hiking tights, with handy zipped bottoms for pulling on and off over hiking boots plus a high snug waistband to keep the tights in place while you’re exercising. Added touches include flatlocked seams and multiple handy pockets. Sold separately.
Picture Organic Clothing milita top and xina leggings
All of Picture’s outdoor-ready clothing is organic and ethically produced, making the brand a great one-stop shop for cold weather gear if you care about the eco credentials of your clothing. This set of base layers have a soft cotton-y feel next to the skin, but are actually made of recycled polyester. The top has a nice boxy cut and handy thumbholes, and the warm, versatile leggings stood out on test – they were some of the most comfortable thermal bottoms we tested, with a wide waistband that stays put when you’re getting active. The cheerful peony print makes this base layer set versatile enough to wear anywhere.
BAM perform bamboo top
Bamboo is one of the newest but also one of the best materials to hit the activewear market – as well as being a sustainable, pesticide-free crop, it naturally lends itself to base layer use, keeping you cool when you’re moving but trapping in heat when you’re staying still. It’s also very soft, making it ideal for sensitive or allergy-prone skin. We love this stretchy top, which is form-fitting enough to trap in heat but is still flexible and breathable enough to wear for fast-paced sports such as running. Stiches are flatlocked, creating a top you’ll barely notice you’re wearing. If you like something thicker, we also love BAM’s quarter-zip sweat, £55, which works as either a base layer or a mid layer.
Columbia engineered half-zip top
If you like to feel as unencumbered as possible when you’re layering up for the cold, this “barely-there” top is for you. One of the stretchiest tops we tested, it’s cut long, sitting on the hips and staying in place when you’re moving. Despite feeling light to wear, it retains heat well, and Columbia’s own moisture-wicking technology effectively does that. It’s a pity the zip on the high neck isn’t covered, so it can be a tad scratchy when fully zipped up.
Finisterre vela top and leggings
Who needs bells and whistles on their base layers when Finisterre makes such simple, smart thermal sets? The top and leggings are made with organic cotton and bamboo, and have flatlocked seams and a small amount of stretch for great comfort – besides that, they are pleasingly minimalist, and the top’s neutral looks work well for casual use as well as for winter sports. Finisterre takes its eco credentials seriously, and as well as using bamboo to create the set, the plastic packaging the base layers come in is water soluble and recyclable. Although sold separately, £90 for both items is a decent price point, too.
Keela torres top
Slip on these base layer and the first thing you’ll notice is how deliciously soft its 100 per cent Merino wool make-up feels. The top has flatlock stitching as well as all of Merino wool’s great qualities – it’s highly breathable, wicks away sweat and is odour resistant. Keela offers a good size range, going up to a size 20, and we love the jewel purple tone, which makes a nice change from boring black base layers. It also scores highly for value for money - we reckon £50 is good value for a 100 per cent Merino top, which can often cost twice that.
Smartwool intraknit Merino 200 crew top
Smartwool, as the name suggests, specialise in great Merino wool layers, and with 50 styles to choose from for women you’re likely to find one you love. Our top pick is Goldilocks-lik and is just right – it feels lightweight but instantly warms your core once you pop it on. It was also the comfiest of all the base layer tops we reviewed, with a lovely knit-like feel that also looks rather smart. It has a longer cut and is very figure hugging, which is great for layering, but if you prefer the looks of a boxier cut we’d suggest ordering a size up. Bright patterned versions and matching leggings are also available.
Haglofs actives wool long johns and top
Haglofs was founded in Sweden, so it’s not a surprise it has an eye for cold weather gear. The no-nonsense 90 percent Merino actives range of base layers is designed with snowsports and hiking in mind, and the top and long johns are form-fitting and easy to layer, with well-placed flatlock seams that mean you’ll barely feel your thermals even as you walk, ski or board. The top works as a wardrobe staple, but the leggings are a little thin to stick on for casual use or a yoga class. The top and bottoms are pricey at £90 each, but we reckon they’re worth it for serious sports lovers, considering they pack a Merino wool punch. Sold separately.
Dare2B divulge core half-zip top
Go bold with your base layers with Dare2B’s cheerful divulge top, designed in a bright floral print. The stretchy polyester fabric feels silky against the skin, and despite a looser cut the top still fits reasonably snugly thanks to stretchy side panels, which also allows you to pop a vest or t-shirt underneath.The half zip is flattering and allows for extra ventilation, and is covered to stop the zip irritating your neck. The base layers aren’t the warmest, and might not suit more ambitious adventures, but they start at just £10.45, making them good choices if you don’t want to spend a lot more.
Helly Hansen lifa Merino midweight hoodie and pant
These are our snug-as-anything top picks for dedicated snowsports lovers. At 225g they’re a nice balance of warmth and weight, and as well as an outer layer of 100 oer cent Merino wool there’s an inner layer of material, which is designed to wick away sweat and trap in body heat, regulating your temperature whether you’re skiing hard or just sat on a lift. The hoodie adds an extra level of warmth for winter, saving the need for a neck warmer and fitting underneath a helmet.
Icebreaker nature dye oasis 200 top
We always rate Icebreaker’s great quality, sustainably sourced Merino layers on test, and they’ve stepped up the ethical offerings with these layers. This top is dyed with plant pigments, an eco-friendly process that uses less water than synthetic dying as well as giving a pleasingly earthy tie dye look. The 200 weight is a good warmth to weight ratio for most outdoor adventure. Icebreaker’s Merino layers are some of the most expensive on sale, but also some of the best, and will last you for years without losing their shape or their warming abilities.
Roxy daybreak top and leggings
If your activewear motto is ‘the brighter the better, then Roxy’s daybreak set is the one for you,which is back for this season in eye-catching floral, graphic and mountain prints. Designed with skiers and snowboarders in mind, these sleek thermals have flatlocked seams and a comfortable lightweight fit that layers up nicely under snowsports clothing and hiking kit. We love the longer length of the top and the slim stretchy fit of the leggings, which would also work well for yoga and gym classes. Sold seperately.
The verdict: Women’s ski base layers
Our top performers are Montane’s versatile primino top and leggings. Finisterre’s simple and comfortable thermal set will keep you cosy all winter, and Roxy’s cheerful daybreak wins in the style stakes.
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