@62 Hello! It's always nice to get outside any time of year and it's even better when you have a friend to go with you!
Do you plan on using some of your buddies gear (tent, sleeping pad, sleeping bag)? If you are, then some of the planning is done for you! If not we've got you covered.
A good place to start in cold weather camping is your clothing. Wearing multiple layers will allow you to stay warm or cool off as you hike or explore the area you are staying. Layering clothing can be a base layer next to skin, a mid layer such as a fleece or down jacket and an outer shell jacket that is waterproof to protect you from wind/rain/snow. Gloves, a hat and a buff are great for keeping any exposed skin warm. As clothing gets dirty or sweaty throughout the day, it can lose some warmth. Take separate clean clothes for sleeping, such as a wool top and leggings.
Don't forget your feet! Wearing wool socks and insulated boots is a good idea, most hiking boots wont have enough warmth unless you are being active. If you will be in snow or wet weather, make sure the boots are waterproof. For sleeping, take a thick warm pair of socks to change into. Wearing a hat and a light pair of gloves will also help you stay cozy throughout the night.
Sleeping! When it comes to picking a sleeping bag, get one that is rated for a colder temperature than you expect to be in. This is because the temperature rating shown in the name of a sleeping bag does not always mean "get a great nights sleep and be toasty warm" it means "this will keep you alive but you'll up all night shivering". If you only plan to sleep in temps around 30 F you will be sleep more comfortably in a sleeping bag rated for a lower temp such as 15-20 F.
A sleeping pad isn't just for comfort, it will actually keep you insulated from the ground! There are many options for sleeping pads ranging from mattress styles to lightweight inflatable pads. I would recommend getting one that is self inflating or contains foam because it will be comfortable and the foam will help insulate you. Sleeping pads also have a rating system called an R-Value. I would recommend getting a pad with an R-Value of 4 or higher. The higher the number the warmer the pad will be.
One trick to stay warm through the night is to heat up some water and put it in a hard sided water bottle/Nalgene. You can snuggle this bottle through the night to stay warm or just use it to warm up your sleeping bag before going to bed! I like to keep one at the foot of my sleeping bag so I don't have to worry about chilly toes!
REI has an Expert Advice article about more cold weather camping tips too! I hope this helps you in getting started, I'm sure more people will chime in with other tips or gear suggestions!
A helpful thing to keep in mind that is pretty applicable to all things cold weather is one of the general principles of of insulation and heat transfer: conduction.
Heat has to escape you by moving through everything between you and the air (clothes, sleeping bag, tent, etc.). The more things you have between you and the air, the better your insulation, but it gets better. The more volume your layers take up (more space), but the less density (less compressed they are) the better.
Think about a down jacket. All that puff works because of little micropockets of air created by the feathers. Heat moves through this slowly as opposed to if the jacket was compressed down to your skin.
This same principle applies to your sleeping bag. Your weight compresses it and it gets less insular on the bottom. Thus a sleeping pad can help. Hammock sleepers discover their backs get cold as well because it's their compressed bag to empty air as opposed to the ground. Underquilts were designed for that specific purpose to hand under the hammock as an insulating layer not affected by your weight.
So when you're looking at gear and the such, don't get tricked into thinking that just because you have put more and more layers on it's the best. You want a balance between weight and insulary nature.
I personally prefer three things.
1) An insulating layer: this will be your skin tight layer. Thermal underwear no top and bottom is the ticket.
2) A warm layer: a fleece jacket or a really good sweater or sweatshirt
3) Your outer shell: this'll be your traditional outdoor weather jacket. Something a bit more waterproof and tough.
You can then shed and adjust as needed.
And never forget a hat! You lose a ton of heat through your head.
Hahaha! Absolutely a typo. Good catch.
To clarify: thermal underwear ON top and bottom. Some folks tend to only think of the lower half with thermal underwear, but you'll be a much warmer camper with the top and bottom.
After all, your bodies source of heat is your chest where your heart is beating. Keep your chest warm and it'll help keep your core temperature up and extremities warm.