A lot of backpackers bring extra clothing on trips that they never wear and end up carrying for no purpose. Doing this has a ripple effect, because it means you need a larger backpack to carry the extra clothing, which is probably going to weigh more.
Instead of bringing extra clothes, I only bring clothes that I know I'm going to definitely wear on a trip, and that in an emergency I can wear all at once!
Putting on all of your clothing at once is also a useful exercise if you've never done it before, because it helps you understand the additive nature of your clothing. In other words, there's no reason to bring along a bulkly 200 weight polypro jacket on a backpacking trip if wearing a 100 polypro sweater, a rain shell, and a wind shirt all at once, will keep you just as warm.
While it sounds bizarre, but being able to do this is a good way to decide which clothes to bring and which to leave at home. If it doesn't serve a unique or specific purpose alone, and one that complements your other clothing, then it's redundant and you should just leave it at home.
For example, here's the clothing I bring on a 3 season backpacking trip:
- Wearing during the day
- Trail runners
- Wool or synthetic socks
- Long pants
- Synthetic boxers
- Short sleeve wicking synthetic shirt
- Light wicking synthetic sweater
- Billed cap
- Ultralight wind shirt, anorak style
- Rain Gear
- Hard shell, breathable rain parka
- Goretex rain pants
- Rain mitts
- Thin polypro glove liners
- Wearing in my sleeping bag (to keep its insides clean)
- Long sleeve synthetic shirt
- Long underwear synthetic bottoms
- Wool or synthetic socks (2nd pair)
- Polypro hat
The nice thing about this list is that I can wear every single one of these items at once if it gets very cold at night.
With so little clothing, the key to staying warm, especially when it's raining, is to keep moving. Your body generates an enormous amount of heat.
If you get cold, you can also simply stop hiking, set up your shelter and get in your sleeping bag until you warm up. If you're still cold in your sleeping bag, you can start putting on all of your dry clothes, including your rain gear, and get back into your sleeping bag. You'll warm right up because you're loosing less heat due to convective heat loss and because your sleeping bag has less air to warm up due to the space your extra clothes will displace.
All of this may sound obvious, but using your clothing together like this is a fundamental concept in the world of lightweight and ultralight backpacking. By harnessing your metabolism and different layering combinations to regulate your body heat, you can eliminate a lot of extra clothing from your backpack that you might be tempted to bring along with you, while still ensuring a healthy safety margin in poor weather conditions.