Staying warm while running comes down to planning and having the right winter running gear. This consists of using layers that allow you to start your run sufficiently warm, but giving you the opportunity to remove the right layers as the run progresses. You will want at least two layers, but might need as many as three. Don't forget the extra accessories you will need for your extremities: head, hands, arms and legs.
When trying to decide how many layers you need, you should remember to allow yourself to be a little cool at the beginning of the run. You will quickly heat up and be shedding layers unnecessarily. You can save yourself extra effort (and extra laundry) if you start off a bit cool. If you are comfortably warm when you start, you will overheat as you get into your run.
Depending one where you run, it may be possible to shed layers on the run. Running at a track gives you this option. Otherwise you will need to plan some way to carry your extra clothing if you should need to shed a layer.
Winter Running Gear: Base Layer
The layer next to your skin is the base layer. This layer should be a fabric that readily wicks sweat away from your body. You should avoid cotton for this layer. Cotton holds the moisture created by sweating, or because of rain or snow, causing you to become more chilled than necessary.
Many of the new fabrics being used in running gear today are called technical fabrics. These are designed to breathe and wick away the moisture. There are various names that each of the tech fabric manufacturers use for their special blend. While some may test better than others in the lab, just about all of them will be a great leap forward from cotton.
Often the running gear sold as a base layer is also a compression layer. It is designed to be worn close to the skin. These can cover the whole body, or be shorts and short-sleeved shirts. Running pants and long-sleeved base layer shirts are available too for colder weather.
Winter Running Gear: Middle Layer
The middle layer is an important layer. This could also be the outside layer depending on how cold it is. This should be a thicker layer than the base layer. Fleece is a good choice here. It will keep you warm while still pulling the sweat away from the body.
If you will not be running long enough to totally drench this middle layer, then cotton is a fine choice. A thick cotton, long-sleeved shirt provides plenty of warmth. But if it gets completely soaked in sweat, then the base layer will not be able to keep you warm.
While this is "the middle layer" you could actually have more than one layer included here.
Winter Running Gear: Outer Layer
The outer layer is used in windy or wet conditions. It is also helpful in extreme cold. This should be a wind protection layer. The cotton or fleece middle layer will keep you warm, but not in biting wind. The outer layer will keep the wind away from your skin.
This is true for rain as well. A waterproof fabric like nylon or GORE-TEX will keep you dry and protect you from wind at the same time.
Winter Running Gear: Extremities
A great deal of body heat can escape through the head. The head is efficient at regulating its own temperature while also regulating the whole body. You don't want to overheat, but you don't want to waste precious warmth through the head either. Wear a cap if the temperature is not too cold. Headbands that cover just the ears can keep them warm while keeping the top of the head uncovered to regulate your body temperature.
When it gets colder, you can move up to a hat that can be pulled down over the ears. There are hats made from tech fabrics, just like other running clothing. But more importantly is that it fit well. If you need it to cover your ears, make sure it is long enough. Having to constantly pull at your hat to keep your ears warm is an unneeded distraction.
Removable running sleeves have become popular the last few years. These are technical fabric sleeves that can be pulled down, or off, when you get into your run. It is like wearing a removable long sleeved shirt. These should only be used if you are not having to wear another layer on top. If you have a third, outer layer, then you will not be able to remove the sleeves.
Gloves can be frustrating to deal with, but are also necessary. Your hands can get cold on a run. But can also be hot inside a pair of gloves. Make sure you have a place to store your gloves while on a run (pocket, or tucked into your pants/shorts). Keep the gloves handy. I find that when running in the winter that I will take my gloves off and put them on several times during a run to keep my body heat regulated.
Winter Running Gear: Treadmill
At some point it may be too cold, wet or icy for you to get out and run safely. Don't forget that it gets darker earlier in the winter too. A treadmill might become your best friend during the winter. Avoid the mistake of calling the treadmill a "dread-mill." Thinking of the treadmill in such negative terms will cause you to despise it even more. There are many advantages of training with a treadmill, not the least of which is keeping you safe and warm during winter running.
Winter Running Gear: Cold Weather Racing
It is not unusual to find the start of a race course lined with discarded clothing during the winter. How can people afford to throw away clothes in this manner? Isn't it an irresponsible waste? One of the ways that you can give back to the community is to donate clothes along the race course. Make sure that the race directors have prepared for the shedding of clothes along the route to be donated to a local charity. But don't throw away your best clothes! I stop by the thrift store a few days before a cold race begins to buy a few items that I can toss along the route.
Don't be afraid to run in the cold. Stop by your local running store to pick up winter running gear. If you are properly prepared then you will be able to run through the cold weather this winter.