A layering system is necessary to keep you warm while being light enough to enable you to undertake a physical challenge.
North Pole MARATHON RUNNING EQUIPMENT
Examples of individual clothing items from various companies are listed / linked below. You can also check out websites such as www.marmot.com , www.patagonia.com , www.mountainhardwear.com , www.eddiebauer.com , and www.taigaworks.ca for further examples / options of appropriate clothing.
The general idea of a layering system on your upper body is that:
1) A base layer will wick sweat away from your body
2) A mid fleece layer will provide insulation, and
3) An outer shell layer will provide protection from the wind.
Only two layers are necessary on the legs (base layer and outer shell) or you will otherwise overheat.
Many adventure / outdoor shops should be very familiar with a layering system and will be able to advise you on what to wear when running in very cold weather.
There are many sample links below highlighted in color - they are examples from a variety of sources and brands of what will work, and , get male or female as applies.
Please Note: It is recommended that you bring two sets of base layers for your legs and torso, and an extra fleece for your torso. You will only wear one base layer on your legs and upper body while running, but you can change into the additional dry base layers during the race if you are getting cold and wet. Keeping dry is important in cold conditions! An extra pair of gloves and socks are recommended below for similar reasons.