Extremely cold air freezes people nearly instantly. Victims are frozen in whatever position they are in when the wave of cold air hits them, lose a bit of skin color, and are covered with some frost.
As taken from Wikipedia: "The plot is centered around a colossal blast of heavily chilled mesosphere air, spreading over the Earth after a solar eclipse combined with the effects of environmental pollution caused a hole in the ozone layer. The catastrophic event threatens to engulf the entire world in ice. As Hobart, Tasmania, is hit by the cold front with temperatures of below -70 degrees Fahrenheit, causing people to die almost instantaneously, physicist Jack Tait (Michael Shanks) tries to find a solution while protecting his family."