Winter hikers and snowshoers often have difficulty staying properly hydrated in cold weather because winter hiking is physically more challenging and the physical act of drinking is more involved than simply sipping from a hydration hose, what with heavy winter gloves and insulated containers.
I usually carry two or three liters of water on winter day hikes, depending on their length, since you can’t count on being able to resupply your water easily. I boil the water for my bottles in the morning to get it real hot, before slipping it into Forty Below insulated water bottle jackets which keep it from freezing for most of the day.
Even then forcing yourself to drink water regularly during the day can be difficult, since your perception of thirst is so different in cold weather than in warm weather. Perspiring in winter is far less evident, even if you’re managing your layering carefully. You also don’t realize that your body is working harder to humidify the air you breathe, which can also drain “your reserves” significantly during the course of the day unless you drink more fluids.
There are two tricks to drinking more than I’ve discovered over the years as a winter hiker and backpacker. The first is to pre-hydrate before reaching the trailhead. Before I start a winter hike, I drink 2 liters of liquid before I even start hiking. I do this by drinking a liter of coffee, milk, and juice over breakfast, and by sipping a liter of water or flavored Gatorade in the car on the way to my hike. I pee more during the day, particularly in the morning, but it lets my body get ahead of the hydration curve rather than falling behind it. I swear by this technique.
The second trick is to add a flavored recovery drink mix to one of liters of water that I carry and to drink it at the beginning of the second half of my hike. My preferred electrolyte additive is Ctyomax which provides me with an easily digested caloric boost without the spiky sugar rush of other drink mixes. I like to think of it as liquid food, which makes drinking an entire liter of water at once a lot more appealing. It even tastes good when the water is still warm.