The base layer is the layer that keeps your body dry, which is extremely important in both winter and summer. Wet skin cools too quickly in winter, potentially leading to serious frostbite, even without immediate awareness! Personally, for a base layer, I exclusively use one brand: Craft.

In the summer, when your skin is saturated with moisture you can't sweat more, which means, you don't cool down. This means your bodies' core temperature will keep rising and you will risk landing into a heatstroke.

Layer 2 is designed to trap your body heat between itself and the base layer, while also wicking moisture away to the outer layer. This ensures warmth, even in extremely cold conditions. For this layer, it's best to choose fabrics with quick-drying and insulating properties, such as merino wool, Polartec, and polyester, all of which are effective choices.

It's important to note that this second layer is typically not used in summer conditions or only as layer 1

Layer 3 is typically used in static situations where you're not moving much and not generating much body heat. This layer is crucial for retaining your body heat and preventing your body from cooling down.

Generally, this layer could be a good woolen sweater or a thick fleece jacket. Materials like alpaca fleece or synthetic fibers both work well. Brands like Revolutionary Race have some great options; I recently bought one myself and can vouch for its quality.

Layer 4 is designed to block wind from penetrating, effectively keeping the cold air out. This can be achieved with a softshell jacket or a breathable rain jacket. While some Gore-Tex jackets are suitable, not all are ideal due to variations in breathability, which largely depends on the number of Gore-Tex layers used. Revolutionary Race has good stuff for all layers.

This layer is particularly crucial in static situations, as wind chill can pose a greater threat than low temperatures alone

Layer 5 is designed to provide protection against rain, keeping you dry. It's especially useful in static situations where you're exposed to rain for extended periods.

Layer 5 can also serve the function of Layer 4 in blocking wind. However, when Layer 4 consists of a softshell jacket, it's advisable to use both layers together for optimal protection. While rain jackets are effective at repelling most rain, it's important to recognize that they do have their limits. Adidas Terrex is the only one that kept me dry for 3 days pouring rain.

Obviously, Layer 6 is designed to protect against rain, but this layer is intended for active, non-static situations. It's raining, but the temperatures are warmer and above freezing.
This layer can be made of Gore-Tex but needs to be breathable since you'll be moving.

Layer 7 serves as the thermal layer, ideal for freezing conditions when you're not moving much. It's designed to be breathable and quick-drying, offering some protection against rain as well. To ensure you stay dry, you should pair this layer with Layer 5.

This combination effectively 'cooks you dry,' as the saying goes. This means that while moisture and air are allowed to escape from inside, rain and external moisture are prevented from getting in.