Dehydration is a danger in cold winter climates that isn't taken seriously enough. We tend to think of hot weather as being dangerous, but cold weather can be even worse.
In the winter the air is often dryer than in most desserts. We lose much of our sense of thirst. Who wants to drink a glass of cold water when they are feeling chilled? Worse, what we do tend to drink is coffee and tea, which are diuretics that tend to dry us out. My lovely wife used to work in a hospital, and most winter patients were at least somewhat dehydrated.
We do tend to sweat in the winter. Snow shoveling, skiing, snowshoeing, splitting firewood -winter activities are vigorous. Dressing in layers can help reduce water loss. As one's activity level increases, outer layers can be shed to keep cool enough to prevent sweating. When at rest, the layers are piled back on.
In the summer, most people have caught on to the idea of carrying a water bottle around. In the winter, it's at least as important, but water freezes. When hiking, I've wrapped water bottles deep in the spare clothes to keep them insulated. A thermos can keep water from freezing for a long time. Keeping water near your body, under your jacket is an old trick. Back in the day, we used to use wine skins because they were fairly flat and easy to wear under a coat. Today there are water bladders that do a good job. Sometimes I'll just keep a few smaller water bottles in my jacket's inside coat pockets.
Never try and rehydrate by eating snow. The energy loss isn't worth it. It takes about the same amount of energy to turn snow into water as to turn water into steam. Your body's core temperature will drop into the danger zone long before your body heat has melted enough snow to yield significant water.
Ever melt snow for drinking water? If you are backpacking, better bring lots of fuel. It's a bit discouraging to stuff a big pot full of snow and only get an inch of water on the bottom. My family used to own a primitive hunting camp. It didn't have much, but it did have a woodstove. Since wood was plentiful, we often melted snow rather than cut a hole in the frozen stream.
Snow melt tastes funky. There's a sort of burnt taste to it. Stirring the snow while it's melting reduces the off taste quite a bit. Running the water through a water filter works too. However, how are you going to keep the filter from freezing?
The key to proper winter hydration is to drink water long before you are thirsty. It takes conscious effort but it's a survival skill worth cultivating. Drink until your urine runs clear. If you start to pee orange, you've waited way too long. If you've been going all day haven't felt the need to pee, that's another indicator of trouble.
One trick is to make sure you are fully hydrated before leaving the warm house. Much easier to drink inside than in a blizzard outside.
Don't let winter's chill lull you into a false sense of security. Drink plenty of water and stay healthy.