I'm interested to note that many posters indicate that as it gets cold they get cold and, once they get to shelter they stay cold.
As a winter warrior that's made a living moving thru some very cold areas ( above the Arctic Circle...yes Ivar...Norway) and remained, possibly not exactly toasty, but comfortable, I have some comments and suggestions.
1. A normal body temperature is about 98 degrees F/63+ C...warm in anyones book. So, how does one stay that way in a cold environment?
Here's a few suggestions:
A. Keep your core insulated (that's the chest area) wear a poly pro t-shirt under any other non-cotton article you may wear (t-shirt/walking shirt). Over that a fleece (short sleeve in temps to 40 degrees F/4.4 C...long sleeve below that), once you start to generate body heat and the air temperature goes up, remove the fleece, but replace immediately if you stop for more than five minutes. Remember, once wet, your body can't dry cotton...therefore, NO COTTON, or at least 50-50% cotton/poly pro.
B. In rain, or sleet put on a water jacket/cape that has openings at the arm pits or chest area...again, once you begin to feel really warm and before you get sweaty...ventilate.
C. Remember, 30% of your body heat vacates the body thru your head. Start your mornings with a wool cap..it works great in wet weather. You get warm...take off your hat!
D. The extremities...fingers when walking, toes and nose when sleeping...while not crucial to survival...are important for a comfortable walk, or a good nights sleep.
E. If you're going to walk in a climate where average temps are 20-40degrees F/-6 C- +4 C at night...a sleeping bag good to 40 degrees is sufficient. Here's the secret about sleeping bags...THEY WORK MOST EFFICIENTLY IF YOU'RE NAKED! Remember...your body temperature is approx. 98 degrees F...If you're already cold and you've piled on the garments...too late to keep from getting cold in the first place...getting into your sleeping bag with all that stuff on...just insulates the cold that much longer. In this case, to regain your warmth...take a warm shower...get into your usual night garments...put socks on your feet, a cap on your head and hold your nose. In a proper sleeping bag...you will get toasty warm. In fact, you may become too warm. So, 1st let go of your nose, then take off your cap and, if you're still too warm...take off your socks. Now you're ready for a good nights sleep. If the temps should drop further, reverse the order of removal.
Now, for the good, or not so good part. If someone in your party is already suffering from hypothermia and their body temperature is dropping rapidly below 98 degrees...the best way to reverse the temp drop and restore proper body temperature is to get into the bag with them...both naked, or nearly so! Works best if you're comfortable with this option. Then again, if it's a case of life or death...deal with it!
Buen got to be warm Camino
Arn