A hiking mid layer is an insulated piece of clothing that generally covers your trunk, arms, and at least the lower part of your neck. It’s meant to go directly over your base layer and provide warmth, if such alone, or with a shell, is not warm enough on the trail. The term ‘mid layer’ can mean different things, depending on if you are using a 3-piece layering system, or a 4-piece system for the winter season.
Mid layer as part of a 3-piece layering system
A 3-piece layering system is just that: a base layer, a mid layer for insulation, and a waterproof/windproof shell. In this case, your hiking mid layer could be anything from thin, moisture-wicking, fleece insulated layer, to a thick puffer jacket.
The 3-piece layering system works good for Spring, Summer, and Fall temperature hiking. But for the Winter season, you may consider bringing 4 layers. Let’s talk about that next.
Mid layer as part of a 4-piece layering system
A 4-piece layering system is similar to the 3-piece one, but there is the option of having two insulated clothing articles between your base layer and shell. The thicker of these layers is, again, your puffer jacket. The thinner of them, which goes under this jacket, is your mid layer. For the purposes of this article, this is what will be referred to as a ‘mid layer’.
However if you do bring 4 layers while hiking, even in the winter, it’s not uncommon for you to just be wearing 3 of them at a time, depending on your activity level, how cold the ambient temperature is, and the weather.
Your mid layer in this particular system is relatively thin for a reason though. Not only should it provide some warmth, but it should also be moisture wicking, and transfer the sweat from the outside of your base layer to the air to evaporate. Keep in mind though, it won’t be as efficient as your base layer in that respect. Still it’s a critical aspect to your thermoregulatory and sweat management system during cold weather hiking.
You should also note that your mid layer should be able to fit under your puffer jacket. This generally means you don’t want your puffer to be tight on you when just wearing a base layer underneath. You want it to be big enough to accommodate your hiking mid layer.
Related: base layer hiking clothing explained
Hiking Mid Layer Design
A hiking mid layer generally resembles a jacket, with a zipper running fully up the front of it, including the collar. But it can also be a pull over, or pull over hoodie. Or it can even be a vest.
Which design works best for you will require some experimentation. But when hiking or backpacking, you need to be able to nimbly thermoregulate on the go. So your best bet is to go for the full zip down style mid layer designs.
Steven from My Life Outdoors talks about using both his pull over, as well as his zip-up mid layer on this Youtube video.
What material should a mid layer be?
A mid layer should be made of a material like fleece, merino wool, or one that is synthetic. But they do make down mid layer clothes as well.
Briefly looking back on the 3-piece layering system once more, if your mid layer is a puffer jacket, it’s probably best for it to be synthetic. That way if your sweat leaches into it from your base layer, it’s less likely to lose its insulation property. Though you might also be able to get away with a down mid layer with hydrophobic down, and a DWR finish.
Fleece
When I envision a hiking mid layer that goes between a base layer and puffer jack, I see fleece. Likely a lightweight or midweight fleece will serve your hiking/backpacking needs, depending on your exertion level, sweat rate, and ambient temperature.
A polyester fleece mid layer will also be breathable, wick moisture, and dry quickly. Outside of these properties, a fleece doesn’t need to be that technical, so you can probably get away with a cheap option if need be.
Is cotton okay as a mid layer?
Cotton material does not make a good mid layer. It holds sweat and moisture which can be dangerous in colder weather. Wet cotton clothing can also add some weight to your person when backpacking.
Hiking mid layer colors
When hiking in the backcountry, or even on less traveled day hikes, it’s best that your wear brightly colored layers, including your mid layer. This helps others see you from a distance, which could be helpful in an emergency or rescue situation. And it also may help bears, mountain cats, and other animals you want to steer clear of, to more readily see you coming in the distance, and maneuver away from you.
When to use a mid layer while hiking
While hiking, you just want to use your mid layer when your base layer, or your base layer and rain shell layer together are not enough to keep your warm.
Don’t start off hiking or backpacking with your insulated layers on
You don’t want to start off wearing your insulated layers, when you first start hiking or backpacking. This is because if you’re already warm outside in these insulated layers, you’re likely going to get hot when you start hiking and generating heat, depending on your exertion level.
And if you’re hot, you’re probably going to sweat. This increases your risk of hypothermia, or at least can make you uncomfortably cold, when you finally stop for a break, or make it into camp if backpacking.
Further, if you start off wearing your mid layer, or that plus your puffer, you’re not going to want to take it off, and go through the hassle of getting out of your pack to stuff it in there, even if you start to sweat.
So it’s best just to start cold on the trail. The dedicated layering clothing manufacture Arc’teryx says you should be ‘comfortably cold’ when starting your hike, and ‘comfortably warm’ when under exertion.
When to use your mid layer at camp
If you’re out backpacking, sometimes it’s best to just bring a second base layer to use strictly at camp. That way you have something dry to change into, for sleeping and hanging out at camp in.
Once you’ve got your nice dry, camping/sleeping base layer on, then you can use your mid layer, as long as it didn’t get drenched in sweat on your way out there. If it did, then just use your puffer jacket as your camping mid layer. And then throw on your shell if you’re still cold.
Your typical camping layering, however, is the base layer, mid layer and puffer jacket combo. Then add your rain shell for wind or rain protection.
Further Reading
Thanks for checking out my article on hiking mid layers. You might also be interested in my winter hiking, camping and backpacking page which has more like articles, or my hiking and camping clothes page.
See ya out there…