def windchill_temp(ta, ws):
    """Calculate the Wind Chill Temperature (WCT) from air temperature and wind
    speed.

    It is the perceived decrease in air temperature felt by the body on
    exposed skin due to the flow of air. It's used by both National
    Weather Service (NSW) in US and Canadian Meteorologist service.
    The formula is derived from Envirnoment Canada [1].

    Note:
        [1]  "Environment Canada - Weather and Meteorology - Canada's Wind
        Chill Index". Ec.gc.ca. Retrieved 2013-08-09.

    Args:
        ta: Air temperature [C]
        ws: Wind speed [m/s]

    Returns:
        twc -- Wind Chill Temperature [C]
    """
    ws_km_h = ws * 3.6
    twc = (13.12 + 0.6215 * ta - 11.37 * ws_km_h ** 0.16 + 0.3965 * ta * 
        ws_km_h ** 0.16)
    return twc
