Wind Chill
Wind Chill is a term used to describe what the air temperature feels like to the human skin due to the combination of cold temperatures and winds blowing on exposed skin. In simple terms, the colder the air temperature and the higher the wind speeds the colder it will feel on your skin if you're outside. So even if it remains the same temperature, but the wind speed increases it will actually feel colder to your skin.
So why does it feel colder if the wind speed increases but the temperature remains the same? The reason is because as wind blows across our bodies it takes the heat we naturally emit and blows it away from our bodies. The faster the wind speed the faster our body heat is taken away and the colder it feels. It is a similar process for when you blow on a hot bowl of soup to cool it down. The temperature that it feels like outside due to the air temperature and wind speed is called the "Wind Chill."
Below is a chart that shows the wind chill for various air temperatures and wind speeds. The colors represent a frostbite indicator, showing the points where temperature, wind speed and exposure time will produce frostbite on humans. Each shaded area shows how long a person can be exposed before frostbite develops. For example, a temperature of 0°F and a wind speed of 15 mph will produce a wind chill temperature of -19°F. Under these conditions, exposed skin can freeze in 30 minutes.
Source: National Weather Service