Wind Chill Concept:
When the wind blows your body loses heat more quickly than if the wind is calm (as long as air temperature is lower than skin temperature). The reason is that each air molecule that touches exposed skin carries away some body heat.
If the wind blows faster, more molecules touch your skin and more heat is removed. This can be enhanced by increased evaporation with higher wind speeds, but wind chill strictly refers to the removal of "sensible" heat, heat that a thermometer can measure.
Heat carried away through the evaporation of perspiration, that kind of heat is called "latent heat" is not part of the original concept.
In external circumstances the `wind chill factor' is such that a temperature of -1° C in still air effectively becomes -18° C if a 40 km/h wind is blowing or if a skier or cyclist is moving at that speed. Windproof overgarments should be worn to avoid excessive heat loss in such conditions.
Heavyweight and thick weave fleece keeps out the wind better than loose weaves.
Loose weaves are not recommended to be worn as an exterior garment in wet or windy conditions since they provide little protection against wind chill.
Sweatpants are a good choice as a base layer topped with a nylon shell. Wind-resistant nylon shell especially made by weaving the fibers extra tightly prevents wind from penetrating the garment and reaching the wearer.
Outdoor safety tips! When the weather is extremely cold, and especially if there are high winds, try to stay indoors. Make any trips outside as brief as possible, and remember these tips below to protect your health and safety.
Check out more safety tips during cold wearther conditions, courtesy of CDC.gov.