Wool or a synthetic against the skin. Cotton holds sweat and then chills you.

Cold weather: middle?

A knit or fleece. This is the layer that actually holds the warmth.

Wind and water. A wool coat for a city, something coated if it will actually rain.

Occasion

What to wear in cold weather

Three layers that each do one job. Warmth is not a thick coat, it is trapped air.

Warmth is not one thick thing, it is layers of trapped air. Three thin layers beat one heavy coat, and they let you take something off when you get on a train.

The three jobs are simple: something against the skin that moves moisture, something in the middle that holds air, and something outside that stops wind and rain. Cotton against the skin fails the first job, which is why you get cold once you have been walking.

Extremities decide how cold you feel. A hat, gloves and proper socks do more for you than an extra jumper, and they take up almost no room in a bag.

The rules, short

Base: Wool or a synthetic against the skin. Cotton holds sweat and then chills you.
Middle: A knit or fleece. This is the layer that actually holds the warmth.
Outer: Wind and water. A wool coat for a city, something coated if it will actually rain.
Extremities: A hat, real gloves, and socks with wool in them. This is where you lose it.

Men