Over the long weekend we went for a walk when the temp was about 50 degrees (F), and there was a slight breeze. I had forgotten about the wonders of layering, but had automatically dressed that way -- a long-sleeved silk and wool blend knit top, a down vest and some alpaca shooter's mittens (all purchased over the years at major discounts from Sierra Trading Post --STP) along with my jeans and boots.
Before long, the vest was snapped around my waist but off my shoulders and torso. Ten more minutes and the mittens were rolled back, then taken off and stuffed in a pocket. 10 more minutes and the vest was tied to the hanging paracord string on my walking stick. By the time we finished, the temp was still around 50, but even my sleeves were pulled up to my elbows. What a great reminder!
For cold weather preparedness supplies, you don't need a bunch of fancy coats and gear, just some carefully selected layers.
Two important things to remember are (1) have a layer next to your skin that is not cotton. Experts will disagree with what that one should be, but they tend to agree that cotton is not a good choice. It holds moisture, which will then drain your heat and make you cold. Cotton can significantly contribute to hypothermia, hence the rule of thumb: cotton kills.
The other thing (2) is that your outer layer should be one that reduces wind and repels water (especially if you are in a wet climate or have enough humidity for dew to form). Wind will suck the heat from your body and insulating layers, but the outer layer also need to 'breathe' enough to let your perspired water vapor escape. I've been trapped in a rubber-lined jacket in cold weather before -- these tend not to breathe. It's a nightmare. It rains or freezes your water vapor inside the jacket. You find yourself trying to manage the build-up of moisture before it makes you wet and cold, rather than managing the activity that brought you out in the cold. You don't need the distraction, plus it can also lead to hypothermia.
Items between the inner and outer layers can be selected according to what you have, what's easy to get and your thermal environment. Here in he southwest high desert, coldest temps are usually well above zero (F) but can get below freezing. Even with the windchill, planning for 20 degrees is normally enough. If you are in Idaho or Montana, you'll need more.
Got an old wool shirt with worn elbows? Instant layer item, even if you cut off the sleeves to make it into a vest. Cheap fleece jacket or vest? Throw it into consideration. Down jacket with chewed-up sleeves at the thrift store? Could be your new down vest! The better the quality the more likely it is to help you keep warm, but you can probably find a bunch of this stuff around the house already.
Don't forget the end of season and after inventory sales. My down vest isn't my first choice of colors or style, but it's warm and I got it new for $13 in a close out sale. Pride doesn't need to be an attribute in frugal preparedness planning.
Below the waist the rules are different. I hate nylon skivvies, but I keep a couple pair in my GO bag. Not only do they keep cotton away from my body, but they also dry faster than cotton in the summer. You'll need something other than cotton under your trousers. I wore LL Bean chamois-lined chinos while living in Michigan's UP, but wasn't living in them in an emergency situation. I did not experience a major moisture build-up even though the lining was cotton - possibly because I did not have another layer over them or because my legs perspire less than my torso and feet. Need some help from readers on their favorite wick-away long-john or trouser warmth solutions.
As for socks, I stick with wool, but in several weights. I had a pair of fancy polypro liner socks years ago when I was X-country skiing in the UP. These days I'm happy with a pair of thin Smartwool under a pair of thicker Smartwool for really cold days. Usually just a single good pair of wool socks works for me. Don't overlook exotic wools if you can get them on eBay or clearance. I have 2 pairs of exceptionally warm baby alpaca socks I got cheap several years ago on clearance from STP. They are amazingly warm and have worn like iron -- mostly with Teva sandals for winter day hikes or around town.
Fellow readers, help us out: what's your temperature environment and layering formula?
UPDATE: PLEASE read the very informative info in the comment from K! Thanks so much for the great addition.