is the sensation of cooling caused by the combined effect of the wind speed with low air temperature. Anyone who has done a walk for a day with relatively low temperatures, noticed that feels colder than the wind if only there. Wind Chill
index is a number expressing the cooling effect of air moving at different temperatures. It also indicates in general, many calories "removed" from the body surface. Normally
body creates a thin layer of hot air which becomes a protective layer of the skin to the air. When there is wind, this removes the layer of hot air leaving the skin exposed to the air cooler. As energy is required for our body reheating the layer surrounding the skin when it is continuously removed by the wind, the temperature of the skin just by downloading and feels increasingly cold.
Calm day (no wind), temperature: 0 º C | But if the wind blows at 10 m / s (35 km / h) Wind Chill is -7 ° C | That is, it feels as cold as it would feel if we were a day with air temperature of -7 ° C and no wind |