How to stay warm
By far, the most important body parts to keep warm are the head and the feet. While it’s a myth that you lose the most heat through your head, you definitely don’t want to leave your head uncovered while the rest of your body is wrapped up. Similarly, the ground will quickly sap your body heat if you’re wearing only thin-soled shoes.
My personal headgear is a soft fleece pullover head cover. I can cover everything but my eyes — though on all but the coldest nights, I have the front pulled down to expose my nose and mouth. Over this I wear a felt hat. I don’t like the down-filled hood of my parka — although it’s really warm — for one reason: When the hood is up, the material rubbing on itself makes so much noise that unless I stand still, conversation is difficult. Also, I just feel better being able to hear what’s going on around me. It’s also worth noting that hoods can diminish peripheral vision — another important safety consideration.
As for boots, go for the best you can get that will let you drive your vehicle. I usually wait until I reach my observing site to change into my cold-weather boots, but you never can tell if an emergency might require you to make a quick exit. My boots are comfortable, light, and have a thick insulated lining in the sole to prevent heat transfer downward. I also recommend pairing them with warm socks of wool or a wool-like synthetic material.
You’ll also want to bring hand-warmers, and lots of them. They’re great when they work but are notorious for not lasting as long as the package says they will. Keep an active one in each of your jacket pockets and slip them into and out of your gloves or mittens to quickly warm up your hands. If you’re wearing gloves, pulling your fingers out of the finger slots can warm them up a lot faster. If your feet get cold, toe warmers are also available, although with the right boots and socks, you shouldn’t need them.
Anyone who has lived in a cold environment knows it’s best to dress in layers. The method that has worked for me starts with light fleece long underwear and pants. (I always opt for pants with lots of pockets to store all my gear close at hand.) To keep my torso warm, I wear a T-shirt underneath a thin, long-sleeved flannel shirt and a fleece zip-up jacket. I top it all off with a down jacket. The last item isn’t cheap, but if you can afford one with true goose down, it’s worth the extra cost.
If you’re particularly sensitive to low temperatures, consider a ski rescue suit as your outer layer. My wife, who feels the cold more acutely than I do, wears one and says it does a great job at keeping the wind and cold from reaching her.
If you’ll be spending the night, pick a sleeping bag with the appropriate temperature range for your area. The better ones are a bit expensive, but get a good one and you’ll be happy you spent the extra money. Here in the desert southwest, we have different requirements than observers in Wisconsin or Norway. Note, though, that most bags advertise rated temperatures that are much lower than the real temperature at which you might feel comfortable. If you take a bag out at its actual rated temperature, you might find its insulation inadequate. This is why veteran campers will tell you to add 15 degrees Fahrenheit (8 degrees Celsius) to a bag’s rated temperature. That will give you the real temperature at which you’ll start to feel cold in the bag. Some sensitive souls may want to add 20 F (11 C).
The worst way to use a sleeping bag is to place it directly on the ground. Even a slight bit of insulation will cut down the amount of heat loss between your body and Mother Earth. I start with a lightweight, plastic, queen-size, fold-out platform that lifts the bag about 18 inches (46 centimeters) above the ground. On the platform, I put a battery-powered, self-inflating air mattress. That raises the bag another foot or so. These two steps make a big difference in comfort, but even a few layers of folded blankets between the mattress and the ground can help.
One item you should always have is a Mylar blanket. Often billed as survival blankets, that’s exactly what it may become. Wrapped around you, Mylar will trap body heat, allowing you to survive all but the most severe conditions. As a cover for your sleeping bag, it will keep you warmer, provide a shield against wind penetration, and keep frost off your bag. These blankets are also waterproof and weigh next to nothing. You can find Mylar blankets at any quality camping or outdoor store, or many places online.