I love camping, but when the temperature starts to drop it can get miserable fast in your campsite. It doesn't matter how beautiful that scenery is, without proper preparations you risk sleepless nights, or worse, hypothermia if you're not ready. The good news though, it's not all that difficult to stay warm no matter how cold it is outside.
Don't push extreme weather
Its common sense, but especially important during winter. Before you head off on a hike or camping trip, do a little research and check the conditions. You need to know the temperatures you'll be facing (especially at night), and if there are any particular storm fronts coming in. My advice is that if it feels dodgy, don't risk it, there's always next weekend.
Create your ideal campsite
Choosing the right site to set up camp is critical in cold weather. You want somewhere that's sheltered from wind chill and the elements, and not in a low spot like a valley or depression. Clear off the snow where you plan to set up your tent, and smooth it all out before the snow starts to melt. Once it does, the icy ground can be impossible to manage later in the day. I'd also recommend gathering enough firewood to keep your campfire going, and setting up a small retaining wall to reflect even more heat into your tent.
Bring the right gear
One of the fastest ways you get cold at night is the ground literally seeps the warmth right out of you. In addition to needing a cold-weather sleeping bag, bring an insulated foam pad to act as a barrier between your body and the ground. A sleeping bag simply isn’t enough. What you're looking for is an aluminumized pad, that has a high R-value (i.e. the higher the value, the better it is at insulating you from heat loss).
Fill your tent
In cold weather you want the smallest tent possible. Every breath you exhale is a loss of warmth, and if you're trying to keep warm inside a massive tent you're not going to be doing yourself any favors. I like to bring all of my gear inside my tent (it also acts as another layer of insulation in the walls), and if you've got a buddy get close to them. The warmth your body's radiate will help heat up the inside of the tent to keep you warm. I'd also recommend using a mylar space blanket as a divider in your tent to reduce the ceiling space. Duct taped to the walls, it makes a big difference when you're reducing the ambient air that needs to be heated.
Use a hot water bottle
The stainless-steel bottle I carry with me when I hike has two functions. Not only does it provide a way to carry water, in the night I can fill it with hot water from the campfire and use it in my bed to warm it up. I usually fill it and put it in while I'm cooking dinner (to warm all of my bedding), and top it up again right before I sleep. Tucked in behind my knees or cuddled in against my belly, the extra heat it radiates makes a big difference on cold nights.
Wear the right clothes
It's common sense to dress in layers when you're camping in the cold, but it's also important you've put some thought into what you'll be wearing at night. The trick is to find a balance, you don't want to be sweating because you're too warm, as it'll soak your sleeping bag and you'll get cold. You want loose fitting clothing, no tight gloves or socks, and remember to buy synthetic fabrics or wool, cotton clothing is a big no-no for cold weather as it doesn't wick away moisture so you get chills.
Don't give in to the wind
With your tent as a first line of defense against the wind, it's important you're doing all you can to protect it from the wind. Though sometimes it cannot be helped, especially if a storm picks up overnight. In addition to finding a campsite that is somewhat sheltered, in bad conditions it may become necessary to continually go adjust and tighten your rigging. I've dropped trees to act as makeshift wind barriers in bad weather, the last thing you want is a ripped tent on a cold winter night.
Remember to snack
You can kickstart your metabolism, and produce a ton of natural body heat by simply eating and snacking throughout the night. I've found a high-calorie protein bar is great right before bedtime, and I've always got a handful of nuts in close reach. Snacking like this gives your gut something to do, and as it breaks down the food it produces heat. Just make sure it's easy, and requires minimal prep, so you can get back to bed and get enough rest.
Always bring a fire starter
If you happen to get cold or have an accident (like breaking through a frozen lake), you need a means to get warm fast. Always carry with you a way to start a fire, even in adverse conditions. I've got a small tinder set that's sealed from any moisture, along with a few strips of magnesium. Even in the rain, this has been enough on more than one occasion to get some damp twigs and kindling burning, so I can gradually build a bigger fire.
Know the signs that somethings wrong
Finally, it's important to know how to recognize when somethings going wrong. Once you start shivering uncontrollably, slurring your speech, feeling a lack of coordination and lethargy, you're probably on your way to hypothermia. If your extremities are looking pale, numb and tingling, there's a chance you're starting to experience frostbite. You need to warm up, and go seek medical attention immediately.
Just because we're in the midst of winter it doesn't mean you can't get out and enjoy the great outdoors. So long as you take the right precautions, pack the right gear and know how to stay warm when camping in cold weather, you can survive no matter what.