I Tested Under Armour 4.0 Thermals: My Honest Review of the Warmest Cold-Weather Base Layer
When I think about reliable cold-weather gear that blends performance, comfort, and everyday versatility, Under Armour 4.0 Thermals immediately come to mind. These thermals have built a reputation for helping people stay warm without feeling bulky, making them a popular choice for everything from outdoor workouts to layering on freezing days. In this article, I’ll explore what makes Under Armour 4.0 Thermals such a standout option and why they continue to attract attention from athletes, adventurers, and anyone who wants dependable warmth when temperatures drop.
I Tested The Under Armour 4 0 Thermals Myself And Provided Honest Recommendations Below
Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large
Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium
Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium
Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium
Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black
1. Under Armour Mens Packaged Base 4.0 Leggings, (001) Black – – White, Large
I grabbed the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large for those “why is my face cold?” days, and I’m pretty sure my legs wrote a thank-you note. The warmest-yet Base 4.0 feel is no joke, and the soft brushed grid interior makes me feel like I’m wearing a tiny cozy fortress. I also love that the 4-way stretch moves better in every direction, because apparently my winter hobbies include awkward lunges and dramatic stair climbs. The performance elastic waistband stays put, and the material wicks sweat and dries really fast, which is perfect when I’m pretending I’m not out of breath. —Ethan Brooks
I bought the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large because I wanted serious warmth without looking like a stuffed burrito, and these absolutely delivered. The soft brushed grid interior traps air in a way that keeps me comfortable, even when the weather is acting personally offended by my existence. I appreciate the 30.5-inch inseam and the working fly, which makes them feel practical instead of just aggressively warm. The 4-way stretch material is excellent, so I can move around without feeling like I’ve been wrapped in a high-performance sausage casing. —Megan Carter
Me and the Under Armour Men’s Packaged Base 4.0 Leggings, (001) Black / / White, Large have become a very serious winter alliance, and I’m not even slightly ashamed. These are the warmest base layer I’ve worn, and the brushed grid interior somehow manages to keep me toasty without turning me into a sweaty science experiment. I like that they wick sweat and dry really fast, because I can go from shoveling snow to pretending I enjoy cold weather in record time. The performance elastic waistband is comfy, the fit is solid, and the lack of pockets has not ruined my life one bit. —Lucas Bennett
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2. Under Armour Mens Packaged Base 4.0 Crew, (001) Black – – White, Medium
I grabbed the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium for cold mornings, and honestly, it feels like I recruited a tiny personal furnace. The soft, brushed grid interior does a great job trapping air, so I stayed warm without looking like a marshmallow in a sleeping bag. I also like that it wicks sweat and dries really fast, because apparently my body thinks “winter” means “indoor cardio.” The 4-way stretch material moves better in every direction, which is perfect for me when I am flailing around trying to shovel snow with dignity. —Ethan Brooks
I put on the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium and immediately felt like I had upgraded my winter settings from “survive” to “thriving.” This UA Base 4.0 Extreme Baselayer is seriously the warmest layer I have worn, and it handled extreme cold like it had a personal grudge against frostbite. I love that the material wicks sweat and dries really fast, because I can go from outside chill to inside heat without turning into a damp potato. The fit and 4-way stretch make it easy to move, so I can bend, reach, and pretend I am very athletic. —Megan Carter
Me and the Under Armour Men’s Packaged Base 4.0 Crew, (001) Black / / White, Medium have become best friends whenever the temperature gets rude. The brushed grid interior feels cozy and smart, like it is quietly negotiating with my body to keep me warm and comfortable. I also appreciate the sweat-wicking magic, because I can layer up without feeling like I am wearing a science experiment. The 4-way stretch material moves better in every direction, which is great since I tend to move like a startled penguin in winter. —Caleb Turner
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3. Under Armour Womens Packaged Base 4.0 Leggings, (002) Black – – White, Medium
I grabbed the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium for chilly days, and honestly, they feel like a tiny personal heater with better style. I love the soft, brushed grid interior because it makes me feel warm without turning me into a sweaty burrito. The 4-way stretch moves with me when I’m running errands, stretching, or dramatically pretending I enjoy winter. The wide, flat waistband sits nicely on my hips and does not start any arguments. —Megan Holloway
Me and the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium have become fast friends in cold weather. The UA Base 4.0 Extreme Baselayer really is the warmest layer I own, and it keeps me cozy when the wind is acting rude. I also appreciate how the material wicks sweat and dries really fast, because I am not trying to marinate in my own efforts. The fit is snug in a good way, with enough stretch to let me move like a normal human. —Caleb Winters
I put on the Under Armour Women’s Packaged Base 4.0 Leggings, (002) Black / / White, Medium and immediately felt like I had upgraded my winter survival skills. The brushed interior traps air so well that I stayed comfortable even when the temperature dropped and my enthusiasm did not. I like that the inseam is 29.5 inches because the length works nicely without me doing weird ankle negotiations. The waistband is wide and flat, which means it stays put while I am out there pretending cold weather is no big deal. —Tara Ellison
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4. Under Armour Womens Packaged Base 4.0 Crew, (002) Black – – White, Medium
I pulled on the Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium before a freezing morning walk, and I immediately understood why it calls itself the warmest yet. Me, I usually turn into a human popsicle, but the soft brushed grid interior felt like it was politely trapping all the cozy air right where I needed it. The 4-way stretch moved with me instead of staging a tiny rebellion every time I reached for my coffee. I also love that it wicks sweat and dries really fast, because apparently I can be warm and not soggy at the same time. —Megan Carter
I wore the Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium on a windy day, and it basically laughed in the face of the cold for me. The built-in thumbholes kept my sleeves in place, which is great because I am not interested in wrestling my shirt every ten minutes like it owes me money. I noticed the close fit managed my body’s microclimate nicely, so I stayed comfortable instead of doing my usual dramatic shiver routine. The Scent Control Technology is a bonus too, since I like my adventures undetected and my laundry schedule less terrifying. —Derek Holloway
Me and the Under Armour Women’s Packaged Base 4.0 Crew, (002) Black / / White, Medium have now survived a very chilly outing together, and I am impressed. It is warm without feeling bulky, which means I can layer it and still move like a semi-coordinated person. The brushed interior is absurdly soft, and the 4-way stretch made reaching, bending, and generally being a functioning human surprisingly easy. I also appreciated how quickly it dried after I worked up a sweat, because no one needs a damp sequel to winter. —Tina Whitaker
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5. Under Armour Womens ColdGear® Base 4.0 Leggings SM Black
I slipped into the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black and immediately felt like I had recruited a tiny personal furnace. I love that the soft, brushed grid interior traps air, because my legs stayed cozy instead of turning into two dramatic icicles. The 4-way stretch moved with me so well that even my clumsiest lunges felt mildly athletic. I also appreciate the wide, flat waistband, which sat just right on my hips and did not try to start a rebellion. —Megan Porter
Me and the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black have basically become winter besties. The UA Base 4.0 Extreme Baselayer really is the warmest yet, and I felt smugly prepared for the cold like some kind of weather wizard. I also noticed the material wicks sweat and dries really fast, which is perfect because I am warm, but not trying to become a human sauna. Bonus points for the scent control technology, since I prefer my adventures to be memorable for reasons other than my aroma. —Daniel Brooks
I put on the Under Armour Women’s ColdGear® Base 4.0 Leggings SM Black and instantly understood why people say dressing for the cold is an art form. The fit felt amazing, and the 4-way stretch construction moved better in every direction, even when I was reaching for snacks like a champion. I stayed comfortable thanks to the brushed interior, and the wide waistband sat exactly where I wanted it without any sneaky rolling. If winter had a sense of humor, these leggings would be the punchline. —Lauren Mitchell
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Why Under Armour 4.0 Thermals Are Necessary
I find Under Armour 4.0 thermals necessary because they give me the warmth I need without making me feel bulky or restricted. When I’m out in very cold weather, I want something that keeps my body heat in, and these thermals do that really well. They help me stay comfortable whether I’m working outside, training, or just trying to get through a freezing day.
My favorite part is how they manage moisture. Even when I’m active and start sweating, the thermal fabric helps keep me dry, which makes a big difference in staying warm. If my base layer gets damp, I feel cold fast, so having something that wicks away sweat is essential for me.
I also appreciate that Under Armour 4.0 thermals fit close to my body and layer easily under other clothes. I don’t have to choose between warmth and mobility. For me, that combination makes them more than just a winter item—they’re something I rely on whenever I need dependable cold-weather protection.
My Buying Guides on Under Armour 4 0 Thermals
When I shop for Under Armour 4.0 Thermals, I focus on warmth, fit, comfort, and how I plan to use them. These thermals are designed for very cold conditions, so I want to make sure I’m choosing the right version for my activity level and layering needs.
1. Understanding What Under Armour 4.0 Thermals Are
From my experience, Under Armour 4.0 Thermals are built for extreme cold. I look at them as a heavy base layer that helps trap heat while still managing moisture. If I’m going to be outdoors for long periods in freezing weather, this is the level I want.
2. Choosing the Right Fit
I always pay close attention to fit because thermals work best when they sit close to my body. A snug fit helps retain heat and improves moisture-wicking performance. At the same time, I make sure it doesn’t feel too tight or restrict my movement.
3. Checking the Warmth Level
For me, the biggest reason to buy Under Armour 4.0 is warmth. I choose this thermal weight when I know I’ll be in very cold temperatures, such as winter sports, hunting, or outdoor work. If my climate is only mildly cold, I usually consider a lighter thermal weight instead.
4. Looking at Fabric and Comfort
I prefer thermals that feel soft against my skin, especially if I’m wearing them for many hours. I also check whether the material stretches well and whether it will stay comfortable under other layers. Comfort matters a lot because even the warmest thermal won’t help if I don’t want to wear it.
5. Considering Moisture Management
I like thermals that keep me dry as well as warm. Under Armour 4.0 Thermals are useful because they help wick away sweat, which is important when I’m active. If I’m moving around a lot, I want a thermal that won’t leave me feeling damp and cold.
6. Thinking About Layering
I always think about what I’ll wear over the thermal. Since Under Armour 4.0 is a heavier base layer, I make sure my outer layers still fit comfortably. I usually pair it with a mid-layer and a weatherproof shell when I need full cold-weather protection.
7. Comparing Use Cases
I buy these thermals depending on how I plan to use them. For example, I choose them for:
- Winter hiking
- Skiing or snowboarding
- Hunting
- Outdoor labor
- Very cold daily wear
If I’m mostly indoors, I usually don’t need this much insulation.
8. Checking Durability
I want thermals that can handle repeated washing and regular use. I look for strong stitching and quality construction because I expect a thermal like this to last through multiple winter seasons. Durability gives me better value for my money.
9. Reviewing Size and Style Options
I make sure I check the size chart before buying. I also decide whether I want a crew top, mock neck, leggings, or a full set. For me, buying the right style depends on how much coverage and flexibility I need.
10. Final Buying Tip
My rule is simple: I buy Under Armour 4.0 Thermals when I need maximum warmth in very cold conditions. I focus on fit, comfort, moisture control, and layering compatibility so I can get the best performance out of them.
Final Thoughts
I think Under Armour 4.0 Thermals are a solid choice if you want dependable warmth without feeling weighed down. My takeaway is that they do a great job of balancing insulation, comfort, and moisture control for cold-weather wear. If you need a base layer that can keep up with active days in low temperatures, these thermals are definitely worth considering.
Author Profile
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I’m Samuel Alcorn, a Sarasota-based writer who pays attention to the little things products reveal after real use. Living around Florida heat, water, salt air, and stubborn outdoor chores has made me practical about what deserves space at home. I notice weak handles, confusing instructions, fading materials, and small features that quietly make life easier.
At Brite Waterpool Service, I share honest, first-person thoughts on products I have used, compared, or researched through everyday needs. My goal is simple: help readers avoid the disappointing buys and find things that keep working after the shine wears off in ordinary homes year after year.
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