Until recently it was unthinkable for me to walk in cold weather in thin pants. C'mon, you gotta wear thick jeans or special winter pants, which are only useful in REALLY cold weather. They're usually bulky and you can't wear only a part of them if it's not THAT cold. In other words: you can't play strip poker for too long. I'm just kidding. ## One pants to rule them all The solution is layers. I've heard about it before, but started applying it only after I've bought pants which quickly became my favourite. At first, I didn't understand it: they're too thin! I can only wear them in the summer! The shop fooled me! But I liked them so much that with time I couldn't even think about wearing something else. So I've just bought underpants for colder seasons. Now I can confidently say I can wear them year round, each and every season. I still can't believe this, really. I'm walking in thin pants in -30° C! They're light: I can wear them even in the hottest summer (40° C). Not to mention spring and autumn. In winter, I can add 1 or even 2 layers of underpants without a problem. Here's my setup. - The outer pants are like "pantalons": they have lots of free space or air. I kinda like it in the summer for this reason, they breathe well and don't stick to your skin. - The bottom layer should be tight as hell but comfortable. It's your second skin. - The base layer: add it in between if it's as cold as in the Ice Age. In my experience, I add it if I'm going to be out and about in the cold for a long time and it's -20 to -30° C outside. If it's colder than that, upgrade some layer to be even warmer: e.g. opt for super warm wool pants or wear a thicker outer shell. Consider a wind and waterproof outer shell. Somehow all of this layering is still more comfortable than all in one bulky pants... Layering also allows me to pack lighter: instead of taking 2 or 3 warm and really bulky pants, I can pack as many light outer shells as I want and as many base layers that I need. The reason is physics. I didn't skip class, and all my physics teachers told me that layers work better than just worm clothes, but I've only understood and applied that years later. 1. Layers of clothing trap air between them, and air is a poor conductor of heat, meaning it helps keep the warmth. 2. When several layers of clothing are worn, each layer traps a new layer of air. This setup increases the amount of trapped air, which enhances the insulation effect 3. Multiple layers slow down the process of heat loss because they increase the overall amount of insulating material (air and fabric) around the body, which works as barriers to heat loss. The same concept is applicable to shirts. For the chilliest winter seasons, take a good fat winter jacket: water and wind proof, and then there are many options: any sweater, long sleeve or hoodie and a one or two base layers. If it's a short trip, consider wearing a base layer plus light outer layer and a winter jacket on yourself and packing one more base and outer layer. You get more options: you can pick and choose layers and you win in size and weight of your baggage, which means you don't have to carry big and heavy bags, or you can take more fancy outer clothes for the sake of variety.