Good points about freezing, usually think of warm weather when it comes to water needs, but cold weather can be just as challenging if not more. You might not need quite as much as in hot weather but just as important to stay hydrated, and hard freezes can make it tricky, especially if it's just cold without much snow. Hydration bags are pretty useless once it gets so cold, you have to constantly be drinking to keep the tube from freezing, and even then if it's very cold it will end up frozen at some point. I end up carrying insulated containers once it gets really cold just to make sure I have at least some water that doesn't freeze. Metal containers are easier to thaw than plastic if they do freeze.