From decades of dealing with the arctic freezes that come to Fort Collins from time to time, I have three ideas for you to consider.
First, you should assess your personal strength and energy. If because of age or illness you have very little physical strength and energy, you are very vulnerable to extreme cold. The extreme cold can and will kill you if you give it a chance. So, stay indoors and only go outdoors when you can immediately enter a warm vehicle which will take you safely to another warm building. Do not travel or venture into the wilds.
For many years, I used my strength and energy to keep me warm during arctic freezes when I had my own newspaper route and later in life when I helped my sons deliver their newspaper routes. That same resource also allowed me to spend hours exercising on our bike trails and snow shoeing in the mountains during winter freezes. I even spent one night in a snow cave with my youngest son.
Second, you need good equipment. You can spend hundreds of dollars to buy coats and other outdoor clothing made with the latest man made materials or you can go to the thrift store or other clothing stores and buy sturdy wool garments. Either the synthetic or the wool can protect you from the extreme cold. In the wool market, some manufacturers taut "smart" wool. "Smart" wool is usually wool from Merino sheep. I do not think that Merino sheep are any smarter than other breeds, but their wool is better for insulating.
As a boy scout leader, I took many boys on winter camping trips. The boys who had good equipment were warm and usually enjoyed the trips. The boys who wore their cotton jeans and other cotton clothing were always cold and miserable. I always tried to educate their parents, but they often resisted by saying that the good equipment was too expensive. I tried to be a good example by wearing surplus wool army pants that I had purchased at the thrift store for $5. Some of those parents were either not listening to me or were to embarrassed to send their kids out in wool clothes from the thrift store. There usually is wool clothing available at the thrift store in boys sizes.
People with good equipment perform well at sub freezing temperatures. Those without good equipment risk frost bite and death.
Third, if you are going to be away from town in the mountains and open spaces take matches and butane lighters in water proof containers in your pockets along with a sharp knife. Before you go, practice making a fire from what nature provides. The main skill is to learn how to go from very small/fine combustibles in graduated sizes to those that are over an inch in diameter in 10 minutes or less. In other words you start with wood shavings made with the knife and/or cotton balls or similar material, then twigs less than 1/8 th inch in diameter, the 1/4 inch diameter, etc. The knife can help you make the different sizes that you need. You simply ignite the smallest and then add the next larger until it ignites and then the next size until it ignites. You keep doing that until the largest that you have will ignite. Once you have done this a time or two, you understand how it works. With the ability to make fire, you have a back up to protect you as you venture into the woods that can save your life if you run out of energy to produce a lot of heat your self, or if your clothing in and of itself is insufficient to keep you warm enough. I built a fire just a few weeks ago to keep my son and myself warm while outdoors in North Dakota.
Hopefully properly assessing your own energy, having good equipment, and being able to make fire will help you survive our freezing temperatures here in Fort Collins.