A blast of freezing Siberian air is being blown towards the UK by an unusual weather event over the North Pole dubbed Sudden Stratospheric Warming (SSW).
The Met Office has confirmed the onset of SSW, which pushes freezing air towards the UK thanks to surging temperatures in stratosphere over the North Pole.
The process causes the polar vortex – a mass of cold air in the upper atmosphere – to split, giving rise to brutally cold conditions in Britain, Europe and the US.
Forecasters believe the cold snap caused by SSW could freeze the UK for weeks with sub-zero temperatures and heavy snow well into March.
A barrage of snow and lows of -22C were recorded when SSW occurred ahead of the cold snap of December 2010.