These are only speculations, raised in case anyone can develop them into something intellectually more solidly grounded or can prove their opposites, but otherwise not worth much for present-day strategy.
Speculation: Perhaps being cold is fatiguing. Perhaps that’s because coping consumes the body’s energy, which exhausts the person. I doubt the effect is huge unless you’re marginal anyway, but allow for it if you’re about to be marginal.
Pneumonia and Cold Air
Speculation: Perhaps a reason people associate pneumonia with cold weather is a high correlation (if there is a high correlation) which in turn might be due to one type of germ that causes pneumonia being better able to survive cold and infect people while it’s cold outside, while other germs causing other pathologies maybe can’t live in such cold environments. Research in about the rhinovirus, causing colds and asthma, suggests that the rhinovirus might reproduce faster in a cold nose because our immune system might be weaker. Whether either is true or not, avoid infection, since cold air alone won’t make you sick that way without the infection.
Oil on Your Skin to Insulate or Even Warm You
Speculation: A source of unknown reliability claimed that one male used “Kwan Loong oil, a . . . liniment for muscle and back pain.” The effect probably lasted only a few minutes. I don’t know about this oil or any other oil on this point, but there was a pair of chemicals (one and maybe both dry) in heat packs for medical first aid, but its heat time was limited, I think to a few hours. You used it by squeezing the plastic bag holding the pair of chemicals until an inner bag broke causing the two chemicals to make contact with each other, resulting in the outer bag soon getting very hot to the touch. The model I saw was maybe six inches on a side, if not smaller, and was rather expensive, making it impracticable for preventing or curing hypothermia. If you’re in an emergency and that’s the best you’ve got, of course use it, but if you’re planning ahead for a trip, taking enough heat packs to cover your body would add a lot of weight and you’d be better off bringing clothing, food, and other supplies instead.
Speculation: A rumor I heard is that some people with the Polar Bear Club insulate their bare skin before wading into a cold ocean by using some kind of automotive grease or oil (I forgot which). Find out how you’d remove it afterwards. Furry animals likely have oil at the base of their fur. The other thing the Polar Bear Club depends on is probably the brevity of their time in the water. Ocean water freezes at about 28.4 degrees Fahrenheit (or -2 degrees centigrade), because the salt lowers the freezing point, but as long as the water is liquid it can’t be less than that temperature. For healthy pepople, the amount of time of exposure while dunked until death from hypothermia might be as short as 15 minutues, but if people on the beach run in and out of the nearly freezing water and are not soaking for more than a five minutes and then warm up in the sun they should completely recover and live to tell about it. Just as a precaution, doing this in a group of people most of whom are healthy and fit and who all go into the ocean in a group that’s close together and will pull anyone who gets into trouble all the way out of the water and up to land even if they can’t help themselves (freak accidents do happen) will be a good safety plan.
Speculation: Someone said they get headaches when they get cold. I assumed something else was the cause but the person seemed not to agree. I can only speculate on how they could possibly be connected. I don’t know the answer.
Warming Whole Body Through Fingers and Toes
Speculation: A rumor is that it’s more efficient to warm your hypothermic body by warming your hands and toes, because they’re small. I don’t think so. They’re small, but what they’d offer for warming is the ease of access to the blood supply traveling through the capillaries, the small blood vessels. But you have those blood vessels in all of your skin. Fingers and toes are susceptible to falling off from frostbite and that's awfully inconvenient. But hypothermia is what will kill you. To fight hypothermia, you should protect head, neck, and trunk. If you need to recover from a severely bad case of hypothermia, warm your whole body, such as by wearing a coat, going indoors, or hugging one or two people sandwich-style (even if they have miserable personalities).