Performance Extra Warm merino wool socks

Performance Extra Warm merino wool socks are knee-high and our warmest socks, made for the very coldest conditions. The merino wool terry construction throughout provides effective warmth for your whole foot and leg, and the strong leg evens out pressure along your shin.

Dispatched the next working day after you order.

Delivery from €5.90. Free delivery on orders over €120.

100-day satisfaction guarantee.

“Choosing the wrong socks backfired one perch fishing weekend, when I forgot to put liner socks under my merino socks. After a kilometre I had a nasty blister on my heel, and the whole competition was in jeopardy.”

Aino Hynnä and Anna Virolainen-Hynnä, members of the Finnish national fly fishing team

Performance Extra Warm – socks you forget as soon as you put them on

Performance Extra Warm merino wool socks solve one of the toughest clothing challenges of the coldest weather: how to keep your whole foot warm when the frost is severe and you are outdoors for long periods. Merino wool is nature’s own smart material. It keeps you warm even when slightly damp and evens out temperature changes. The all-over merino wool terry construction traps warmth around the whole foot, not just the sole, because cold reaches your feet from every direction.

Merino wool is a highly breathable material that wicks moisture and helps keep your feet dry. For the best insulation and dryness, wear a thin merino liner sock underneath, such as the Performance Liner sock: the liner wicks moisture away from the skin, and Extra Warm provides the warmth. This keeps your feet warm and dry even on the longest trips in freezing weather.

Merino wool is naturally odour-resistant, so you can wash your socks less often and they last longer. When you take them off at the end of the day, you are not greeted by that familiar end-of-day smell. Instead, they feel fresh. On long trips, you can often freshen them up simply by airing them – a big advantage when washing is not an option.

Performance Extra Warm merino socks come with a 100-day satisfaction guarantee. We want you to have time to try the socks properly: wear them as normal for 100 days. If you are not satisfied with them for any reason, you will get your money back.

Professionally tested Performance Extra Warm merino wool socks for every situation

The shaped knitted heel fits your foot precisely, so the sock does not twist or move inside your footwear. Strong Lycra knit along the full length of the leg spreads pressure evenly down the shin, so the knee-high leg stays up all day without the tight marks you get from an ordinary ribbed cuff. No more socks that slip off or need a second thought.

The all-over merino wool terry construction is at the heart of these socks. Soft wool loops line the whole sock, not just the sole, and trap warmth all around your foot. This is exactly what makes Extra Warm our warmest sock. These socks are made for the moments when the frost is at its hardest and your feet need protection from every side. The toe seam is flat and unobtrusive, so you will not feel that familiar pressure point on top of your big toe, even after a long day. It is a small detail you only notice when it is missing.

Performance Extra Warm is designed for the very coldest conditions: winter hikes, jobs in freezing weather and long days outdoors when the temperature drops well below zero. With these socks, you can even head north for a midwinter hike and keep your feet warm.

In Svala AIR System™ layering, Performance Extra Warm belongs to the Accessories range, which complements the main layers. While the Zero Layer and Base Layer manage moisture and warmth around your body, merino wool socks complete the system by keeping your feet warm and dry. A warm body needs warm feet too.

Thoughts from the designer

“People often think the cold only gets to your feet through the ground, so the extra warmth goes into the sole of the sock alone. In reality, cold reaches your feet from every direction. I wanted a sock with soft merino terry covering the whole foot and lower leg, and a leg that spreads pressure without squeezing. For the hardest frosts, this is our warmest solution. To get the most out of it, wear a thin merino liner sock underneath.”

Ninni Pohto, designer at Svala

Materials with a purpose

Performance Extra Warm merino socks are made from a soft merino wool blend: 74% merino wool, 24% polyamide and 2% elastane. The high merino wool content provides warmth, breathability and natural odour resistance, polyamide adds durability, and elastane adds stretch that keeps the sock in place.

The key feature of these socks is the all-over merino wool terry construction: soft wool loops line the whole sock and trap warmth all around your foot. This makes Extra Warm the warmest sock in our range. The shaped knitted heel and strong Lycra knit along the full length of the leg improve the fit and spread pressure evenly down the shin.

Merino wool is a highly breathable material that prevents sweaty feet and helps keep them dry. Long-fibre merino wool does not itch like ordinary wool, so the socks feel soft even on sensitive skin. For the best insulation, wear a thin merino liner sock underneath, such as the Performance Liner sock.

The merino wool in these socks is NATIVA™-certified, which means it is traceable and responsibly produced on mulesing-free farms. All materials meet the OEKO-TEX 100 standard, which guarantees the product is safe for skin contact.

We recommend washing merino wool socks before you wear them for the first time, so they fit true to size. Please note that merino wool socks may shrink slightly in the wash. Reshape and stretch them firmly while still damp to restore their original size. The socks are made in Finland by Sukkamestarit, using responsibly produced merino wool and decades of experience.

Developed in Finland for Finnish weather

Heading north for a midwinter hike? Spending long days in biting cold? Looking for the warmest possible merino socks for the harshest conditions? Performance Extra Warm is made for these moments.

Svala merino products work for almost any exercise, everyday or leisure activity. Your gear will no longer hold you back from enjoying the outdoors.

Performance Extra Warm merino wool socks are at their best in these situations:

Winter hiking in severe cold
Trips and wilderness treks in deep snow
Cross-country skiing and winter activities
Ice fishing
Snowmobiling
Clearing snow and outdoor work in severe cold

Svala merino products are developed in Finland and have been tested in professional use for decades. This means they have been put to the test by people who are hard on their clothes: on long work shifts, on week-long wilderness trips and in wet, cold conditions where your gear decides how comfortable your day is. If the socks can survive them, they can survive you too.

Clothing layer	Accessories
Temperature-range	−30 °C to −5 °C, as part of a layering system or on its own
Season	autumn, winter, and spring
Colour options	Black/grey
Material	74% merino wool, 24% polyamide, 2% elastane
Manufacturing	Sukkamestarit, Finland
Material origin	Uruguay / Italy
Labels & certifications	Key Flag Symbol
Care instructions	Read the merino wool care instructions here.

Svalan pyöreä tunnus, jossa lukee 100 päivän merinovillatakuu ja Svala of Finland.

100-day satisfaction guarantee

Our products have been developed over many years by leading professionals in collaboration with experts in various activities. We are so confident in the quality and comfort of our products that we can offer a 100-day satisfaction guarantee on all our products.

Use the product as normal for 100 days. If you are dissatisfied with the product for any reason, you will receive a refund.

Frequently asked questions about the product

How does the Performance Extra Warm merino wool sock differ from the Performance Warm High merino wool sock?

Both are knee-high and very warm, but they are built differently:

Performance Warm High has a four-layer construction in the foot, with an innermost layer of moisture-wicking polypropylene, and a thin leg. It is made for winter activities and active outdoor use.
Performance Extra Warm has a merino wool terry construction throughout the entire sock, which makes it the warmest sock in our range.

Choose Warm High when you want warmth and effective moisture wicking while you're on the move. Choose Extra Warm for the very coldest conditions, when maximum warmth matters most. Wear it with a thin liner sock to wick moisture.

Why do you recommend wearing a liner sock under the Performance Extra Warm merino wool sock?

The inside of the Performance Extra Warm merino sock is merino wool throughout, which makes it exceptionally warm. Because the sock is mostly wool, you get the most out of it when you wear a thin merino liner sock underneath: the liner wicks moisture away from your skin, and Extra Warm takes care of the warmth. This keeps your foot dry even when it sweats, so it doesn't get damp in the cold.

As a liner, we recommend the Performance Liner sock, for example. Combining two socks also reduces chafing, because the friction happens between the socks rather than directly against your skin.

Will such a thick sock fit into my shoes?

The Performance Extra Warm merino wool sock is a thick, warm sock, so it needs room around it. Wear it with roomy winter boots or generously sized hiking boots that leave space for a thick sock. Ideally, there should be enough room in your shoe for air to circulate too.

A shoe that is too tight compresses the sock, so it doesn't keep you as warm, and the pressure can even make your foot colder. A warm sock works best in roomy, well-fitting footwear.

Do the socks get clean at a low washing temperature?

Yes. The socks get clean even at a low temperature, as long as you use a good-quality detergent and a suitable wash programme. A high temperature is needed less often than people think – dirt and microbes come out well on a delicates cycle too, as long as the detergent does its job.

The recommended washing temperature is based on the merino wool in the socks. Wool fibres shrink, felt and get damaged easily in a hot wash, so a lower temperature isn't just enough – it's also the right way to keep your socks in good condition for longer. Besides merino wool, the socks contain other fibres that could handle a hotter wash, but it's best to care for the whole sock according to its most delicate fibre: the wool.

Merino wool also does its part: it naturally resists odour, and its ability to repel dirt keeps the socks fresher for longer. In practice, this means you need to wash the socks less often, and a low washing temperature is usually more than enough.