What's the scientific reason it's so cold out?

The '13 / '14 winter was colder and stormier than usual in in the mid-Atlantic because 1) a quasi-stationary ridge of HIGH pressure took up a position along the west coast of the US and 2) the polar vortex shifted south to a position over south central Canada.. These features directed a steady flow of frigid arctic air masses into the central and eastern US. (see image - the wind blows parallel to the lines)

The leading edge of these cold air masses reached the Gulf of Mexico (GOM) where the sharp contrast between the arctic air and the warmer air over the Gulf created favorable conditions for storm systems to form. The storms migrated NE out of the GOM where they produced above normal snowfall over many stations in the mid-Atlantic.

Here in the UK we are in the northern hemisphere of the Earth, a little bit more than halfway between the equator and the North Pole. That means that we have our winter at the end of the year, between the end of November and the start of March.