12 of the best kids' thermal sets to keep away the cold | The Sun

WITH temperatures starting to drop down into single figures, a cosy set of base layer thermals is an essential addition to your child’s winter wardrobe. 

Whether you're lucky enough to be planning a family ski trip, or you just want to keep your kids a little bit warmer in the chilly school playground, these thermal layers offer children and toddlers extra protection from bitter winter weather.

Designed to be worn as a base layer under trousers and thick coats, thermals are specially engineered to use your child’s own body heat to insulate against the cold, while also working to remain breathable and wick away sweat.

Although kids’ thermals are often designed with skiing, snow and winter sports in mind, they have many other uses too. Children’s base layers are ideal for kids who feel the cold when you’re out and about, or during outdoor PE lessons.

They can also double up as a particularly cosy set of pyjamas on very icy nights, and many are stylish enough to be worn on their own as a single super-snuggly layer too.

What to look for in kids thermals

There are a few features to look out for when shopping for kids thermal layers as these will help to increase comfort, warmth and practicality. 

Look for thermals with flatlock seams, as these will reduce chafing and ensure little ones stay comfy. Elasticated waists and cuffs around the wrists and ankles help to keep base layers firmly in place even while building snowmen or hurtling down a hillside on a toboggan. Tops with a dipped hem around the waist are also useful as they stay tucked in and stop skin exposure even when bending and moving.

Merino wool or man-made fibre thermals?

Most kids' thermals are made from either a cotton/polyester mix or merino wool. There are pros and cons to both, so consider what would work best for you and your child.

Merino wool is a beautiful natural fibre that is incredibly soft (never itchy, promise) and a great choice for children with allergies. It’s also wonderfully warming, naturally, temperature regulating, breathable, moisture wicking and antimicrobial, so less cleaning is needed.

However, it can be a little trickier to wash, it may be slightly less hard wearing and it is often more expensive than man-made fibers too.

Cotton and polyester mix thermals provide plenty of warmth, are very hard-wearing, moisture-wicking, easy to wash and quick to dry, and are usually on the cheaper end of the spectrum.

However, you may find that they aren’t quite as soft, need to be a little tighter for moisture wicking to work effectively and are not quite as breathable,  so polyester layers may need to be washed more often too.

Best kids thermals at a glance:

  • Best kids thermals for cosiness: Nordic thermal merino kids top and leggings by Polarn O. Pyret
  • Best budget kids thermals: Wedze Kids Ski Base Layer Top and Bottoms at Decathlon
  • Best kids thermals for winter sports: Kids' HH Lifa Merino Base Layer Set by Helly Hansen
  • Best mid-price kids thermals: Thermal Base Layer Top and Bottoms from Muddy Puddles
  • Best thermals for very young children: Kuling dotted baselayer top and dotted baselayer pants
  • Best kids thermals for a range of ages: Lani kids' base-layer set by Reima
  • Best luxury kids thermals: Kids Adventurer Jogger Set by Iksplor
  • Best kids thermals in a variety of fits: UNIQLO

Lani kids' base-layer set

  • Lani kids' base-layer set, £43.58 by Reima – buy here

This is the go-to kids' thermal set from outdoor Scandi brand Reima, and as a result, it is available in five different colours as well as a huge variety of sizes from toddler to teen. It has been constructed with active kids in mind and as a result there’s lots of lovely attention to detail. 

Flat seams provide comfort, the elasticated waist keeps the bottoms secure and the lightweight Thermolite® material transfers moisture away from the skin, keeping kids comfortable, no matter how trees they climb or slopes they conquer. We really loved the bright sunny yellow colour we tested and the fact they’re easy to wash and care for too.

Wedze Kids Ski Base Layer

  1. Wedze Kids Ski Base Layer Top at Decathlon – buy here
  2. Wedze Kids Ski Base Layer Bottoms £4.99 at Decathlon – buy here

Ideal for kids who spend a lot of time out on a frozen sports field, this simple black polyester set from Decathlon may look fairly utilitarian, but it has some nifty features. 

The high neck on the top keeps away any chills and there are also breathable panels between the shoulder blades and behind the knees to prevent active kids from overheating.

It is quite tight fitting and a little thicker than some of the other sets we tested, but there’s a decent amount of stretch, which, as the name suggests, is great for winter activities such as skiing. Plus, as you get a whole thermal set for under a tenner, you really can’t argue with the price.

Polarn O. Pyret

  1. Nordic thermal merino kids top, £28 at Polarn O. Pyret – buy here
  2. Nordic thermal merino kids leggings, £28 at Polarn O. Pyret – buy here

Providing the perfect combination of attractiveness and practicality, this gorgeous fairisle print set, from renowned Swedish brand Polarn O. Pyret,  is available in both mint green and pastel pink. 

Made from sustainably sourced merino wool, the leggings and top are both fine enough to reduce bulk, yet still super snuggly. This set benefits from cuffed sleeves and ankles and can be easily tucked into winter boots, the top also has a dipped back, so there’s no danger of exposing any bare skin to the elements.

Marks & Spencer

  • 2pc Thermal Cotton Blend Set, £15-17 at Marks & Spencer – buy here

This set from high street giant M&S is available in a range of fun Disney prints from Frozen to Spiderman – all of which were big hits with our tester and clearly had instant appeal for kids.

The fabric is a mix of cotton, viscose and polyester and is soft, warm and has a little stretch to it too. Although not as toasty as some of the other thermals we have tested, we still loved the cosy cuffs and that fact it boasted responsibly-sourced materials.

Helly Hansen

  • Kids' HH Lifa Merino Base Layer Set, £55 by Helly Hansen – buy here

Combining the best of both worlds, this thermal set from performance specialists, Helly Hansen features two layers: merino wool for breathable warmth and their own ‘lifa’ material (an engineered polyester), designed to quickly wick moisture away. Our little tester was warm and snuggly, even in biting cold winds and there were no signs of overheating either. 

The reinforced fleece knees and elbows feel lovely and would be great for kneeling and playing in snow (do you want to build a snowman?) and both items fit brilliantly too.


  • Kids Adventurer Jogger Set, £176 by Iksplor – buy here

From the merino wool experts Iksplor, this stunning 100% merino wool set really is the ultimate piece of gear for little adventurers. 

The fabric itself is buttery soft and it is great at temperature regulating, so you can step from stuffy indoor climes to freezing outdoor winds without any issue. It’s 100% merino wool, so it’s moisture-wicking and antimicrobial, meaning less cleaning is needed, but don’t worry it can be tossed in the washing machine too. We loved that the top is really long and hooded, plus it's UPF 50 so it keeps little ones protected from bright sunny mountain weather too.

As it is a jogger set it can easily be worn as a mid layer, or on its own for days when comfort is key (it would make a fab travel outfit, for example). 


  • Kuling dotted baselayer top, £26 at Alex and Alexa – buy here
  • Kuling dotted baselayer pants, £21-25 from Alex and Alexa – buy here

Made with slightly younger children in mind, this incredibly soft merino wool set is really cosy with natural temperature-regulating properties (so no clammy skin) and flatlock seams.

The simple unisex design is definitely cute enough to be worn on its own, potentially as stylish separates. Unlike a lot of other thermal sets on the list, this one doesn’t have cuffs, which might be handy if this is something your child particularly objects to.

Mountain Warehouse

  • Jacquard Kids Merino Base Layer Set, £39.99 from Mountain Warehouse – buy here

Available in both unicorn and dinosaur print these base layers really do have all the bases covered.

They are made up of a 50/50 merino wool and polyester mix so they have the wool benefits of being naturally antibacterial, quick wicking, drying and insulating and they also have flatlock seams and reinforced cuffs to help little ones stay warm and comfy. 


  • Darley Kids Thermal Set, £21 by Tog24 – buy here

This wonderfully affordable set is an essential addition to your child’s winter wardrobe. Made from 100% polyester, it is soft, stretchy, and quickly works to wick away any sweat. The simple black design is ever-so-slightly ribbed and it has flatlock seams too. 

We loved the simple design of this set which is neutral enough to be worn as part of a PE kit and lightweight enough to go under lots of layers without getting bulky.

Muddy Puddles

  • Thermal Base Layer Top £20 at Muddy Puddles – buy here
  • Thermal Base Layer Bottoms, £20 at Muddy Puddles – buy here

Available in four different unisex colours with an adorable timeless moon print, this set is designed to last and be passed down again and again. Made from a mix of cotton, Spandex, and polyester materials, they are highly breathable and moisture-wicking and have the benefit of being slightly easier to wash and care for than some other wool options.

We absolutely loved the fit of these thermals and the cool contrasting cuffs on both the leggings and top, which also have thumb holes, so, no cold mitts here! 


  • FIX merino wool long johns with allover print, £24.99 at LINDEX – buy here
  • FIX merino wool top with allover print, £24.99 at LINDEX – buy here

This cuddly top and long johns are available in either brown or blue and are covered in cute little squirrels and acorns. They are made from 100% merino wool, so are warm, breathable and yet still lightweight. 

We love the slim fit and thicker cuffs around the wrists and ankles, which prevented these thermals from riding up,, no matter how many layers you piled on top. 


  • Kids Heattech Ultra Warm Crew Neck Long Sleeved Thermal Top, £14.90 at UNIQLO – buy here
  • Kids Heattech Ultra Warm Thermal Leggings, £14.90 at UNIQLO – buy here

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Japanese brand Uniqlo have nailed it again, combining their signature basics with their own brilliant thermal innerwear. Their clever, comfy, bio-warming Heattech material (a mix of polyester, acrylic, viscose, and elastane) promises to use moisture released by the body to generate heat when it's needed most. 

Our testers certainly stayed warm and toasty, even in blasting winds and the simple design appealed to slightly older children. There’s also a whole range of fits, sleeve lengths and necklines depending on their preferences and they’re affordable enough that you can buy a few options to mix and match.

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