As high pressure becomes established over the UK and repositions itself over Scandinavia - we lie in an extensive easterly airflow drawing in exceptionally cold air from northern Russia (Siberia).
Cold air streaming from the east like this has often been nicknamed the "Beast From The East".
This has been described as record breaking cold polar continental air.
It's looking to be one of the most extreme examples of it's kind in years.
From the weekend, expect severe frosts by night and temperatures to struggle above freezing by day.
There's also likely to be some snow forecast - primarily for eastern areas
A biting bitter wind chill will make it feel icy cold. The wind chill will be numbingly cold.
As we approach March we'll be in a deep freeze - we're not used to such deep-set cold.
We see this scenario every two to three winters, but this time the situation is more intense.
Last time we had such a set up was January 2013 which brought very cold air from late January to Easter.
That was the coldest start to Spring since the 1980s, when temperatures were below freezing with snow falling as far south as London and the Isle of Wight at the end of March.