What is the Beast from the East?
The 'Beast from the East' is a phrase used to describe cold and wintry conditions in the UK as a result of easterly winds from the near continent.
When pressure is high over Scandinavia, the UK tends to experience a polar continental air mass.
When this happens in winter, cold air is drawn in from the Eurasian landmass bringing the cold and wintry conditions that give rise to the 'Beast from the East' moniker.
What does it mean for the UK weather?
The characteristics of the air depend on the length of sea track during its passage from Europe to the British Isles. The air is inherently very cold and dry and if it reaches southern Britain with a short sea track over the English Channel, the weather is characterised by clear skies and severe frost.
With a longer sea track over the North Sea, the air becomes unstable and moisture is added giving rise to showers of rain or snow, especially near the east coast of Britain.
The UK’s lowest temperatures usually occur in this air mass, lower than minus 10 °C at night, and sometimes remaining below freezing all day.
Polar continental air only reaches Britain between November and April; at other times of the year the source region is neither cold nor snow-covered and winds from north-eastern Europe bring a form of tropical continental air.